The main objective was to find a predictive model for the development of the jaw in patients with the most frequent facial cleft malformation, i.e. complete unilateral cleft lip and palate (UCLPc) by means of multivariate methods. This prediction is urgently needed from the clinical aspect. It will make it possible to provide early detection for patients at risk of adverse development. The study is based on a long-term X-ray cephalometric follow-up of 73 boys with UCLPc during puberty. Prediction was performed by methods of multiple regression and regression partitioning trees. The best equation predicts the intermaxillary relations at 15 years of age with high reliability (determination coefficient R2 = 0.822). The model was successfully verified statistically. In clinical practice, we suggest the use of a simple method of regression partitioning trees where the measurement of only 1 to 4 dimensions in a ten-year-old patient would suffice to achieve a reliable reading of the ANB angle at 15 years of age from a tree diagram.