The study was designed to examine the gender-related differences in maximum mechanical power output in various short-burst activities during growth. The subject sample consisted of four subgroups: 9 boys (14.11±0.6 yr), 9 boys (10.67±0.71 yr), 7 girls (14.29±0.49 yr), 7 girls (10.57±0.54 yr). We meausred peak power (PP), mean power (MP), fatigue index (FI) during 30-s WAnT, squat jump height (SJH) and power (SJP), and counter movement jump height (CMJH) and power (CMJP), maximum speed over 20-metre distance (S20). Lactation concentration was measured in the 3rd and 5th minutes after the WAnT. Ratio normalisation and ANCOVA were used to remove the influence of the differences in muscle (MM) and body mass (BM). Male adolescents had higher absolute values of PP (P<0.05), MP (P<0.05) than female. Ratio normalisation showed that boys had higher PP/BM (P<0.05), PP/MM (P<0.05), MP/BM (P<0.05), MP/MM (P<0.06) than girls. The ANCOVA adjustment for MM showed differences between genders in PP (P<0.001), MP (P<0.001), SJH (P<0.05), SJP (P<0.05) and CMJP (P<0.001), whereas the ANCOVA adjustment for BM showed differences only in PP (P<0.001), MP (P<0.001). Prepubertal boys had higher absolute values only in SJP (P<0.05). We concluded that variations in body composition could not be the only key to gender-related differences in power output in short-burst activities.