Background: The aim of this study was to develop and validate a questionnaire designed to assess the patient's affective, cognitive, and perceptual state during treatment administration. Methods: 362 individuals (214 females, 148 males, mean age 54.6 years) with predominantly musculoskeletal or dental problems participated in the study. Patients responded to the questionnaire immediately following a treatment. The questionnaire included items of 9 proposed scales devised to assess mood, psychological tension, sleepiness, mental absorption, treatment appraisal, perceived cooperation during treatment administration, perceived somatosensory intensity of treatment as well as negative and positive bodily sensations during treatment. Treatments were administered in 2 spa centers, a clinic for physical medicine and rehabilitation and a clinic for dentistry. Treatments investigated were among others dental treatment, massage, packs, baths, relaxation training, exercise, and acupuncture. Results: The proposed scales were confirmed. Scales had adequate to good reliability and validity. All scales significantly distinguished between treatments. Conclusion: The devised questionnaire has adequate properties to assess patients' experiences during treatment administration.