Abstract This study examines the concerns and beliefs about medication reported by patients with nonmalignant chronic pain encountered within general practice. Two hundred thirty-nine patients with chronic pain took part in this research. Patients completed the Pain Medication Attitudes Questionnaire, a measure of patient concerns and beliefs relating to addiction, withdrawal, side effects, mistrust in doctors, perceived need of medication, scrutiny from others, and tolerance. The data revealed that patient concerns and beliefs predicted general medication nonadherence. In addition, concerns were related to the direction of nonadherence: overuse of medication was related to increased perceived need for medication and greater concern over side effects; underuse was related to decreased concerns over withdrawal and increased mistrust in the prescribing doctor. Analyses also indicated that patient attitudes and concerns about medication were more predictive of nonadherence than both level of pain and the reported frequency of experienced side effects. This research contributes to the increasing evidence that patient attitudes and beliefs about pain medication are associated with adherence behavior. Training general practitioners to identify and address these concerns may reduce concerns, improve adherence, and facilitate the doctor–patient relationship. Patient concerns about medication predicted nonadherence, including both over- or underuse. Concern appeared more predictive than both pain intensity and frequency of side effects experienced.