Objective: To determine the optimal dentoalveolar measure to assess unilateral cleft lip and palate (UCLP) patient plaster models. Design: The models of 34 patients with UCLP taken at 5, 10, and 15–20 years of age were scored by two examiners on two separate occasions using five indices: the 5 Year Olds’ (5YO), GOSLON, Modified Huddart/Bodenham (MHB), EUROCRAN, and Overjet. Reliability, validity, and ease of use were recorded for each index/examiner. Setting: All models were scored in either Bristol Dental Hospital or Derriford Hospital, Plymouth, United Kingdom by senior orthodontic clinicians. Results: Highest overall reliability was seen with MHB (Kappa = 0.56–0.97). Predictive validity was similar for MHB, GOSLON, and 5YO with a 50–65 per cent prediction of final outcome from 5 and 10 years. EUROCRAN palatal index showed no clear predictive validity (Spearman’s correlation = 0.20–0.21). Agreement to the gold standard 5YO score at the 5-year age group was high for MHB (Kappa = 0.83) and moderate for GOSLON (Kappa = 0.59). Agreement to the gold standard GOSLON score at 10 years was highest for 5YO (Kappa = 0.69), followed by Overjet (Kappa = 0.59) and MHB (Kappa = 0.46). Time to score 34 models per index (minutes): GOSLON (13.4) < Overjet (13.6) < 5YO (19.4) < EUROCRAN (24.8) < MHB (27.4). Conclusion: As an outcome measure of UCLP models, only MHB and 5YO indices can be recommended for use at 5 years of age and GOSLON at 10 years of age.