This study employed social judgement theory to identify and determine the relative importance of factors influencing occupational therapists' subjective decision making when managing children and adolescents with cerebral palsy and upper limb hypertonicity. An extensive literature review was conducted to identify potential factors that might be used. Two clinical experts were then asked to review and refine these factors. Finally, 12 experienced occupational therapists who had worked with people with cerebral palsy for at least 5 years were asked to add or exclude factors and then to rank them. Thirty-seven factors that might influence therapists' decision making were identified and ranked. The reason for referral and family's goals were ranked as the first and second most important factors respectively. Agreement among therapists was significant, but low (Kendall's W = 0.38; p < 0.0001). When participants were divided into two groups, those who were very experienced (mean = 13 years, SD = 6.95) and those with less experience (mean = 5.6 years, SD = 0.55), the ranking of the factors did not differ significantly. These findings are discussed with respect to research in clinical decision making, the training of occupational therapists and the education of students.