Recently, there is an increasing number of different dietary supplements available on the market and the percentage of their use increasing among population of professional and amateur athletes. Dietary supplements are considered to be nutritional or physiological preparations intended to further enrich the usual diet for the purpose of maintaining health.There is a lack of researches in Croatia on the use of dietary supplements in professional and especially among amateur athletes. The main goal of this study was assess the use of dietary supplements in professional and amateur athletes and also their choaches as well as the knowledge of this population about dietary supplements. A total of 301 subjects, aged 15-57 years, participated in the study. The data were collected through questionnaire specially created for the purpose of this research, which contained 45 questions divided into four sections. The results showed that dietary supplements are used by a large proportion in both,professional and amateur athletes (84 %), professionals 87.5 % and amateurs 76.9 % respectively. The most commonly used were protein supplements (23.3 %), followed by vitamins (21.5 %) and minerals (17.4 %). An analysis of the knowledge about dietary supplements showed that the knowledge of the supplements is inadequate, especially within trainers who have been detected as an important source of information on those products.