There is a need to understand the mechanism through which homework contributes to clinically meaningful change in therapy. Theoretically meaningful factors such as willingness to complete therapeutic assignments and cognitive skill acquisition have not been carefully studied in prior research. Depressed outpatients (N=46) received cognitive behavioural group therapy for a 10-week period and were assigned relevant homework activities. Patient self-report and independent ratings of homework compliance were obtained on a session-by-session basis. Using path analysis, the authors found evidence that willingness to complete homework assignments and mastery of skill in cognitive restructuring helped account for the relationship between homework compliance and reduced symptom severity (R2 =.40). However, paths were only significant when patient self-report of homework compliance was used in the model. The present study highlights the problems in assessing homework compliance and in assuming that independent assessment of compliance is more accurate than patient self-report.