tObjective: To identify the prognostic factors for conventional physical therapy in patientswith chronic low back pain (CLBP).Methods: Prospective observational study.Participants: One hundred thirteen patients with CLBP selected at the Spinal Disease Outpa-tient Clinic.Main outcome measures: Pain intensity was scored using the Numeric Rating Scale (NRS), andfunction was measured using the Roland-Morris Disability Questionnaire (RMDQ).Results: The Fear-Avoidance Beliefs Questionnaire work subscale results (FABQ-work; oddsratio [OR] = 0.27, 95% confidence interval [CI] 0.13–0.56, p < 0.001) and extraspinal pain(OR = 0.35, 95% CI 0.17–0.74, p = 0.006) were independently associated with a decreasedresponse to conventional physical therapy for CLBP.Conclusion: We identified high FABQ-work and extraspinal pain scores as key determinantsof a worse response to physical therapy among CLBP patients, supporting the need for aspecial rehabilitation program for this subgroup.