Main goal of this research is to determine relative age effect (RAE) on young croatian taekwondo athletes. Data is collected during the realisation of project under Croatian Scientific foundation called „Anaerobic capatities in kicking combat sports“ (2014.-2018.). 259 competitors from Croatian cadet taekwondo championship 2015. are representing research sample. Sample consists of both male and female competitors with birth date from 2000. to 2003.. For research purposes sample is divided into two separate sub-samples: a) medal winners (n=72) and b) other athletes (n=187). Variables sample consists of name, surname, sex, date of birth, weight category and success status/medal won. Data analysis was conducted with nonparametric Chi-square test which gave us certain results. There is no asimetry between observed and expected frequencies according to birth date of all competitors (χ 2 = 12.28, df = 11, p= 0,34). Analysis of sub-sample medal winners determined existention of statistically significant difference between observed and expected frequencies according to their birth dates (χ 2 =45.31*** d.f. = 3, p = .00***). Analysis of won medals suggests declining trend in addition to birth years, with 36 medals won by competitors of 2001. birth year, 27 by 2002. birth year and 9 medals from competitors of 2003. Birth year. Conclusion of presented results is that presence of mentioned trend can lead to mistakes in initiation and selection of young competitors in taekwondo. Categories between competitors should be reconsidered and differences eventually minimized. Categorization should be more specified in matter of age which would lead to more fair competition and minor effect of relative age on result success.