OBJECTIVES: The performance of daily activities is a major challenge for people with chronic obstructive pulmonary disease (COPD).  The 65-item Functional Performance Inventory (FPI) was developed to quantify these difficulties in naturalistic studies and clinical trials.  The instrument was based on an analytical framework of functional status and qualitative interviews; it was reduced to a 32-item short form (FPI-SF) through a systematic process of item reduction and testing and re-formatted for greater clarity and ease of use.  This study assessed the content validity of the FPI-SF. METHODS: Qualitative cognitive interviews were performed with men and women with COPD recruited through pulmonary clinics in the United States.  Interviews were conducted in-person by a trained interviewer using a semi-structured interview guide and continued to saturation.  Qualitative data analyses included the following: 1) comprehensiveness; 2) clarity of instructions, items, and response options; 3) respondent interpretation of the instructions, items, and response options; 4) ease of completing the questionnaire; 5) relevancy of the items; 6) formatting (e.g., design and placement of instructions, font, placement of items on page); and 7) identification of new concepts (e.g., functional areas or activities that patients consider relevant and not represented by existing items). RESULTS: Twenty COPD patients were interviewed: 12 (60%) males; mean age = 63.0 ± 11.3 years; 14 (70%) Caucasian; 12 (60%) retired; mean FEV1 = 1.5 ± 0.5 liter; FEV1% predicted = 48.4 ± 13.1. Content of the FPI-SF was seen as comprehensive and represented activities participants found important and often difficult to perform.  Participants understood the instructions, items, and response options as intended.  No new concepts were identified.  Two minor formatting changes were suggested to improve clarity. CONCLUSIONS: These results, together with its development history and previously tested quantitative properties, suggest the FPI-SF is content valid for use in clinical studies of COPD.