Poor medication adherence is an important issue in the pharmacotherapy of chronic diseases. The hypothesis is that rate of adherence in phatmacotherapy of chronic diseases in Croatia is low, less than 50 % and that it depends on several factors such as: age, education, type of disease, polytherapy as well as understanding of purpose of the treatment and instructions provided by physician or pharmacist. Patients and pharmacists have different approach toward the importance of adherence in long-term therapy.The aim of this reasearch was to determine level of adherence in longterm therapy in city of Zagreb, investigate relationship between socio-demographic and clinical parameters and adherence, determine the reasons for non-adherence as well as to investigate attitudes of pharmacists and patients regarding adherence. In this research patients' medication adherence was measured by using two, the most commonly used metods for measuring medication adherence: self-reported questionnaire and pharmacy data claims with calculating Medication Possesion Ratio (MPR). As questionnaire Čulig scale was used. This scale with very good internal consisteny (Cronbach α= 0,89) is suitable for measurement of adherence to all chronic diseases and was originally developed for the purpose of this research. Patients' medication adherence measured by self-reported questionnaire (635 participants) was 41,7% and when measured using pharmacy claims (150 participants) data was 37%. It was found out that patient’ attitudes toward therapy and relationship with physician have greater impact on patient medication adherence than sociodemographic characteristics and that the main reason for non-adherence is forgetfulness.. The results of this research shown that the counselling role of pharmacist is not recognized by patients.