We used three-dimensional computed tomography (CT) to define the bony configuration of the acetabulum and the proximal femur and their relationship to complicated and/or neglected congenital hip dislocations and Legg-Calvé-Perthes disease. Three-dimensional CT was useful for preoperative planning and postoperative evaluation of hips with complex deformities, which were often difficult to assess by means of plain radiographs or conventional two-dimensional CT. The coverage of the femoral head under the acetabular roof and the severity of the hip dysplasia could be assessed easily with three dimensional CT, and acetabular and femoral torsion could be measured.