Relaxation and guided imagery are useful strategies for cancer pain; however, their effects vary from patient to patient. Patients' perceptions of these treatments and factors that contribute to their effectiveness have not previously been described. Data from interviews conducted after a trial of guided imagery and progressive muscle relaxation (PMR) interventions were analyzed to compare patients' perceptions of treatment effects with observed changes in pain scores, and to explore patients' ideas about factors that contributed to the effectiveness of each intervention. Post-study interviews were conducted with 26 hospitalized patients with cancer pain who had completed trials of guided imagery and PMR. In most cases, participants' perceptions of treatment effects matched observed changes in pain scores. Participants described treatment and patient characteristics that influenced effectiveness of the interventions such as active involvement in the intervention, guided instructions, providing a source of distraction, stimulating relaxation, individual abilities and preferences, and pain qualities.