The purpose of this study was to determine the optimal inner-shoe volume for children tennis players. Sixteen participants, aged from 8 to 12 years old assessed comfort of 6 shoes, which were a combination of 3 lasts (thin, medium and wide) and 2 upper constructions (flexible and stiff), while a sock equipped with textile sensors was measuring the pressure applied on their foot. The thin last was based on the proportion of an adult last. The widest shoes produced the lowest pressure on the 1st and 5th metatarsal heads, the medial midfoot and the medial and lateral heel (p < 0.05), whilst they were perceived the most comfortable for the 3rd and 5th metatarsal heads, the 5th metatarsal base and the medial and lateral heel (p < 0.05). These outcomes indicated that footwear manufacturers should design wider shoes for children than for adults