This investigation examined factors related to adherence to treatment regimens for children with cystic fibrosis (CF) and their mothers. Subjects were 45 children with CF who ranged in age from 6 to 10 years and their mothers. Findings revealed that children's and parents' reports of level of adherence were related to their knowledge of the specific details associated with medically prescribed treatments. In this sample, 12% to 32% of mothers did not have an accurate understanding of physician recommendations for their children's treatments. When controlling for individual differences in the prescribed treatment regimens, parents' and children's knowledge of what had been prescribed accounted for a significant portion of the variance in the children's reported treatment-related behaviors. Results are discussed in terms of implications for future intervention research aimed at enhancing adherence to treatment as well as for future directions for clinical efforts in this area.