This study compared the measurement properties of the Moorehead‐Ardelt quality of life questionnaire‐II (MAQOL‐II) and the BODY‐Q, to determine which was more suitable for measuring patient‐reported outcome (PRO) in Danish bariatric surgery (BS) and body contouring surgery (BC) patients. We examined content validity against the COSMIN guidelines and compared psychometric performance using Rasch measurement theory methods and criteria. MAQOL‐II data were obtained from the Danish Bariatric Surgery Database from September 2010 to November 2017, and BODY‐Q data were collected from June 2015 to March 2018. The MAQOL‐II failed to meet recommended standards for content validity, while all criteria were met for the BODY‐Q. A total of 16 965 MAQOL‐II and 2259 BODY‐Q assessments were obtained. A random sample was selected from the MAQOL‐II dataset to match the BODY‐Q sample. Psychometrically, the BODY‐Q performed better than the MAQOL‐II. For example, Cronbach's
αwas 0.82 for the MAQOL‐II vs ≥0.90 for all BODY‐Q scales. Fifty percent (3/6) of MAQOL‐II items had disordered thresholds, while all BODY‐Q items had ordered thresholds (123/123). Poor item fit was revealed for 17% (1/6) of MAQOL‐II and 8% (10/123) of BODY‐Q items. For scale reliability, person separation index was 0.79 for the MAQOL‐II and 0.88 (0.81‐0.93) for the BODY‐Q. In conclusion, the MAQOL‐II does not meet today's standards for a rigorously developed PRO measure. The BODY‐Q, on the other hand, gives substantial, accurate and interpretable measurement and should be recommended for use in PRO in BS and BC patients.