One thousand nine hundred and eighty-four children who had received conservative treatment for shaft (diaphyseal and metadiaphyseal) fractures of lower limbs (1162 femoral, 822 tibial fractures) at an average age of 8.5 years (range 0–14 years) were reviewed by clinical and radiographic investigations at an average follow-up of 6.6 years (1–15 years). Particularly, two main features were evaluated: remodelling of (angular and rotational) deformities and post-traumatic overgrowth. Mechanisms underlying these processes are discussed, based on a review of the literature, and parameters conditioning their evolution are analysed. Finally, criteria for an acceptable reduction (and limits for residual deformities that may be tolerated) at the time of conservative treatment are proposed.