This report is a comparative study of the treatment results after secondary and late secondary bone-grafting in cleft-palate patients with residual cleft in the alveolar process, operated with surgical technique as described by Krantz Simonsen. 293 bone-grafted cleft-palate patients are included in the study. Marginal bone-level, periodontal state of teeth adjacent to the cleft-region, recurrence of oro-nasal fistula together with possibility of total dental rehabilitation (i.e., morphology of alveolar process in cleft region and amount of attached gingiva) have been used for evaluation of the treatment results. The best results are seen in the youngest group of patients, and based on the results of the present study, bone-grafting is recommended immediately before eruption of the canine in the cleft-region.