OBJECTIVES: The objectives of this study were to examine whether progressive medical conditions lead to greater use of complementary and alternative medicine (CAM) as compared with more stable conditions, to see whether disease severity influences CAM use, and to identify the main motivations behind CAM use. METHODS: Subjects were selected from outpatient clinics at Hotel Dieu Hospital. Surveys were conducted by mail and telephone. Medical diagnosis and severity were obtained from medical files. Statistical tests included chi, Kruskal-Wallis, and correlations. RESULTS: One hundred ninety-four children were surveyed. The "progressive" group included 15 patients with Duchenne muscular dystrophy and 22 patients with cystic fibrosis. The "nonprogressive" group included 85 patients with cerebral palsy (CP), 49 with diabetes mellitus, and 23 with spina bifida. Twenty-three percent were using CAM. CP had the highest use; diabetes mellitus had the lowest. Popular therapies included massage and dietary/herbal remedies. Progressiveness had no impact on CAM use. Within the CP group, greater disease severity was associated with higher use (P < 0.001). The main reason for CAM use was to complement conventional medicine. CONCLUSIONS: Disease progressiveness had no impact on CAM use, but severity within the CP group did. Complementing conventional medicine was the main motive. Understanding the reasons and patterns of use of CAM is beneficial in efforts to improve the care of children with chronic medical conditions.