Following the separation of spouses, a family undergoes a reorganization process where the choice of a formula for child custody represents a major step, which child's living environment will depend on. Despite the importance of this form of custody, it seems, in the context of the crisis following separation, that decisions surrounding that choice are often taken haphazardly, without much consideration of various alternatives. On a different note, the family's profile at the time of the separation is bound to change following the pace of the child's and the parent's development. What may seem a relevant formula for a three year-old child may not necessarily be the case when the child turns eight. This article looks at the extent to which the child custody formula evolves to adjust itself to the changing needs of children and parents. Research focused on a sampling of 112 families separated for an average of four and a quarter years, with children aged 10 (N = 49) or adolescents of 15 years of age (N = 63). Data was compiled through a telephone questionnaire filled out by the parent who was the most committed to the child's custody. The description of the two categories of change (minor and major) was made according to the original child custody formula, the time lapse since the separation, the child's age and parental re-composition. Results point to three main trends: a) child custody arrangements do not evolve much over time; b) when there are changes, these are especially motivated by the needs of the parents; and c) the changes mainly result in reducing the frequency of contacts between the child and the parent without custody.