Substances of nanometre dimensions, i.e. nanoparticles, are increasingly present in cosmetic products. The most common requirement for using nanoparticles in cosmetics is to improve the delivery of cosmetic ingredients to the skin. Nanoparticles can also be used to stabilize cosmetic preparations. Titanium dioxide and zinc oxide nanoparticles are used predominantly in sunscreen cosmetic preparations, because they effectively block UV radiation and provide formulation transparency, which is pleasing to the consumer. Silver nanoparticles are used in cosmetic products as antibacterial agents or preservatives, although nanosilver is currently not listed in Annex V, of EU Cosmetic Directive, as being an approved list of preservatives that can be used in cosmetic products. Despite the obvious benefits, the use of nanoparticles in cosmetic products increases potential safety issues. From the security aspect, it is most important to find and give precise answers to questions about the type and stability of nanoparticles in the product, then about the potentials of their absorption into the viable parts of the skin and through the skin into systemic circulation, the type of exposure and their formulation in cosmetic products. Significant efforts are being made in international harmonization on the definition and safety of nanomaterials in cosmetic products. This is important for manufacturers, advertisers and end users of cosmetic products. In this paper, available literature on the definition, use and safety of nanoparticles in cosmetics are presented, as well as regulatory aspects. Also results of a questionnaire are presented, on the perceptions and attitudes of consumers in the Republic of Croatia, on the use and safety of nanoparticles in cosmetics. OBJECTIVES Provide a comprehensive overview of literally available knowledge on the definition, use, safety and regulatory aspects of nanoparticles in cosmetics and examine the perceptions and attitudes of consumers in the Republic of Croatia on this issue. The research could contribute to the development of guidelines for formulating and marketing advertising of cosmetic nanomaterials. METHODS In searching literature and collecting relevant data for the development of this work, online databases (PubMed, ScienceDirect, Google Scholar) and reports and guidelines of leading regulatory bodies, agencies and associations, such as the European Commission, the European Chemicals Agency and Cosmetics Europe were used. Relevant articles were analysed analytically, with the highlights of the most relevant ones, along with the discussions and conclusions that were used to shape own point of view of studied theme. The key words used in the research are: "nanoparticles" and "nanomaterials" in combination with the words „classification“, „production“, „cosmetics“, „dermatology“, „skin“, „mechanisms“, „penetration“, „absorption“, „toxicity“, „properties“, „structure“, „types“, „systems“, „transport“, „activity“, „claims“, „influence“, „health“, and „regulation“. An online survey questionnaire was created to obtain consumer opinion. Google Forms was used as a tool for creating and processing questionnaire data. Questionnaire was sent, in the form of an access link, to respondents by e-mail, and made available through LinkedIn network and web forums Forum.hr and Žena.hr. The survey included the adult respondents of both genders, residents of the Republic of Croatia. The survey was anonymous, and the collected data were used exclusively for the development of this work, which is clearly stated in the questionnaire. Only valid and fully filled questionnaires were considered. The questionnaire consisted of 20 questions, of which the first five questions related to the data of the respondent (gender, age, education, place of residence and affiliation with the topic of the questionnaire). The next 12 questions concerned the understanding of the survey topic and the perception and attitudes about the use and safety of nanoparticles in cosmetics. A total of 300 people was surveyed, and as all respondents were adult, residents of the Republic of Croatia, and correctly filled the questionnaire, all 300 completed questionnaires were considered for data processing and final report. RESULTS The advantage of using nanoparticles in cosmetic products is to improve the stability of ingredients, effective skin protection against harmful UV rays, aesthetically pleasing product, and deliver of active ingredient to the desired site with its controlled release for prolonged effect. Despite the obvious benefits, the use of nanoparticles in cosmetic products increases potential safety issues. Harmonizing dermal nanoparticle absorption methods and systematization of key physicalchemical parameters need to be harmonized in order to clearly understand their link and role in dermal absorption. Regarding the regulatory aspect, nanomaterials are regulated, but the European Commission continuously gives its opinion and evaluation of the regulation of nanomaterials and their impact on people and the environment, and a continuous complement to the existing regulation is expected. The analysis of the respondents showed that there is a large share of the population that does not understand or is not well acquainted with the subject, which causes wrong interpretations and fear of the presence of nanoparticles in cosmetics. CONCLUSION The use of nanoparticles in the cosmetic industry is increasingly present. According to many indicators this is an unstoppable process and the future. What must not be diminished is the importance of continuous research and evaluation of impacts on human health and the environment. The regulation is continually amended, as new knowledge and evidence emerge, but it is extremely important at the same time to educate the public in the proper manner, so that fear and negative attitude will not be unnecessarily raised. Manufacturers have the task primarily to respect the regulation and to fulfill all their obligations, both manufacturing and sales ones. Marketing advertising is an essential factor in creating consumer confidence, so regulatory communications must be respected, but first, analysis of their attitudes is a key part of marketing campaign design.