PURPOSE: The purpose of this study was to gain insight into how low back pain (LBP) patients conceptualize the construct of expectations regarding treatment. METHODS: This study was nested within a mixed-method randomized clinical trial comparing three primary care interventions for LBP. A total of 77 participants with LBP lasting longer than 6 weeks were included; semi-structured interviews were conducted querying patients about their expectations for treatment. Also factors influencing their expectations were explored. Interviews were administered following enrollment into the study, but prior to study treatment. Two researchers independently conducted a content analysis using NVIVO 9 software. RESULTS: LBP patients' expectations could be categorized in two main domains: outcome and process expectations, each with subdomains. Patients expressed expectations in all subdomains both as values (what they hoped) and probabilities (what they thought was likely). In multiple subdomains, there were differences in the nature (positive vs. negative) and frequency of value and probability expectations. Participants reported that multiple factors influenced their expectations of which past experience with treatment appeared to be of major influence on probability expectations. CONCLUSION AND RECOMMENDATIONS: This study showed that LBP patients' expectations for treatment are multifaceted. Current measurement instruments do not cover all domains and subdomains of expectations. Therefore, we recommend the development of new or improved measures that make a distinction between value and probability expectations and assess process and/or outcome expectations covering multiple subdomains. Some of the influencing factors found in this study may be useful targets for altering patients' treatment expectations and improving health outcomes.