There is a lack of knowledge and reliable measurement instruments to assess excess skin after massive weight loss. The purpose of this study was to test the reliability of a new self-administered questionnaire. A self-administered questionnaire, the Sahlgrenska Excess Skin Questionnaire (SESQ) was designed to assess excess skin after weight loss. The questionnaire includes 30 questions about demographic data, activity and daily life and excess skin on specific body parts and the body as a whole. Forward and backward translations were made by two independent professional translators, from Swedish to English and then back to Swedish. The questionnaire was tested on 10 patients from Sweden and England and was followed by an interview with each patient. Minor corrections were made. A test-retest was carried out to evaluate the reliability by sending the Swedish questionnaire to 46 subjects with weight loss after obesity surgery, dieting, or medication. The test-retest reliability of questions concerning activity and daily life between the two occasions had a Percentage Of Agreement (POA) of 49%-76% and a weighted Kappa of 0.44-0.78. The questions about the degree of excess skin on specific body parts had a POA of 50%-76% and a weighted Kappa of 0.53-0.81. Excess skin perceived as causing problems had a POA of 32%-57 %, an adjusted POA of 63%-87%, and an Intra-Class Correlation of 0.72-0.92. The SESQ is reliable for evaluating patients' experience of excess skin after massive weight loss.