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STUDY DESIGN Cross-sectional and longitudinal designs within a prospective cohort study. OBJECTIVE Translation of Hannover Functional Ability Questionnaire (FFbH-R) into Norwegian and examination of its factor structure, internal consistency, reproducibility, construct validity, and responsiveness in patients with long-lasting back pain. SUMMARY OF BACKGROUND DATA Several condition-specific instruments have been developed to evaluate functional status in low back pain, but FFbH-R was the only instrument found to solely measure perceived capability of performing daily activities. METHODS Recommended guidelines for translation of questionnaires and quality criteria for validation were followed. A total of 111 patients (aged 18-65 years) with long-lasting back pain were consecutively recruited from an outpatient spine clinic. Two additional samples of patients with long-lasting back pain were added into the exploratory factor analysis, giving a total number of 224 patients. Predefined hypotheses regarding construct and longitudinal validity (responsiveness) were examined. RESULTS Factor analysis indicated that 2 items should be removed, resulting in a 3-factor solution as the best fit. The factors were related to flexibility, dynamic strength, and posture endurance. Satisfactory internal consistency and reproducibility were demonstrated for the total and subscales of the Norwegian version of FFbH-R. Most of the predefined hypothesis regarding construct and longitudinal validity were confirmed, and discriminate ability was shown. Minor floor and ceiling effects were demonstrated. CONCLUSION Psychometric properties of the Norwegian version of FFbH-R were satisfactory in patients with long-lasting back pain, but the dynamic strength and posture endurance subscales might be complemented with additional items.