The topic of this research paper is the examination and analysis of the duration of tennis matches in different age groups between girls and boys. The research follows all matches that took place during 2 different weekends, i.e. a total of 4 days of competition. All achieved results were included in the official competition ranking by the Croatian Tennis Federation, taking into account the age of the players. The analyzed sample consists of 101 matches. In the under 12 tournament 46 matches were played, while in the under 10 tournament 55 matches were played. The necessary statistics were collected from these matches. Along with analyzing the differences in the duration of matches between the genders, the duration of matches played in the knockout phase was also observed. It can be concluded by analyzing the statistics from the sampled matches that the differences in the duration of matches between genders in the tournament for children that are under the age of 12 are negligible. The value of p is 0,95 which is higher than 0,05 (p>0,05). This proves that the differences in the length of both the girls’ and boys’ matches are minimal. In the tournament for children under the age of 10 a statistically relevant deviation is noticeable between the length of the matches in which the boys participated compared to the girls. The value of p is 0,01 which is less than 0,05 (p<0,05) and that proves that there is a noticeable difference in the duration of the matches played depending on the players’ gender.