Background: In spite of studies reporting a relatively high frequency of additional conditions in children with a cleft lip and/or cleft palate (CL/P), almost no research has focused on this clinically important subgroup. The objective of this study was to compare psychosocial adjustment in children with CL/P with and without an additional condition. Design: Cross-sectional data based on routine psychological assessments at age 10 years, with comparisons to national reference groups. Setting: Centralized treatment, Norway. Participants: Two hundred five children with CL/P (participation rate: 80.1%) from three consecutive birth cohorts. Outcome measures: The Strengths and Difficulties Questionnaire (self-report and parent report) and the Child Experience Questionnaire (self-report). Results: Eighty-one children (39.5%) were identified as having at least one condition in addition to the cleft. These children reported significantly more psychosocial difficulties than children with a cleft alone. Differences between specific conditions were minor. Children with a cleft alone (n = 124) reported mean scores that were comparable to those reported by the reference group. There were no differences in adjustment between children with a visible versus a non-visible cleft. Conclusions: The present study highlights the need for research to be conducted in children with CL/P who have additional conditions to provide better knowledge and clinical care for a potentially vulnerable subgroup of children and their parents.