Sports activities can constitute a factor in improving postural control. The aim of this study is to compare static balance in the tandem stance between female artistic gymnasts and non-training girls. This was performed with and without visual control, as well as in a position with open eyes, on a 1.25 m high platform. Two groups of thirty girls participated in the study. The first group consisted of gymnasts (mean age 9.50 ± 1.20 years, body height 133.50 ± 11.40 cm, and body mass 28.90 ± 6.90 kg), while the second group comprised non-training girls (mean age 9.80 ± 1.20 years, body height 142.60 ± 10.90 cm, and body mass 37.40 ± 9.70 kg). Balance measurements were taken using the CQ Stab 2P two-plate stability platform. In the measurements conducted with the subjects’ eyes closed, the gymnasts obtained a lower value for displacement regarding the maximal centre of pressure (COP) in the anterior–posterior direction and a higher frequency of COP displacement (p < 0.05). In the trial performed on a platform, a greater COP displacement frequency was found among the non-training girls (p < 0.001). Differences in the values of the variables characterising the static balance of gymnasts and non-training girls were revealed only in conditions of increasing difficulty concerning the motor task (increasing the height of the position and/or without eye control).