The objective of this study was to describe a numerical scoring system for the measurement of maxillary arch constriction in patients born with unilateral cleft lip and palate (UCLP). A modification of the Huddart/Bodenham scoring system was compared and contrasted with the current methods of measuring treatment outcome, the GOSLON and 5-year indices. The GOSLON and 5-year indices are represented by 10 sets of study models grouped into five categories representing the range of possible outcomes in terms of dental arch relationship, with two sets of models in each of the five categories, whilst the modified Huddart/Bodenham method uses the frequency and severity of crossbite of the dental occlusion to evaluate maxillary arch constriction. The latter system was found to be more objective and reliable, and to correlate well with current recommended standards. It was also more versatile and more sensitive to interarch discrepancies. However, further work is required to refine it to reflect the potential for orthodontic treatment to mask interarch discrepancy following surgery.