Self-report methods are commonly applied in medicine and psychology. However, their diagnostic value in assessment of patients with acquired brain damage can be limited due to a number of various difficulties encountered by these patients, including cognitive disorders, fatigue, similarity of psychopathological and somatic symptoms, psychological reaction to the disease and limited or lack of insight (anosognosia). In our article we highlight the most important limitations of application of popular frequently used questionnaires in evaluation of brain-injured patients. We also discuss possible ways of adjusting self-report techniques to requirements of diagnostic process in this clinical population. Proposed modifications refer to, among others, specific construction of diagnostic tools (appropriate content and number of questions, methods of measuring responses), collecting information from relatives, using questionnaires along with more objective measures, and controlling conditions in which the assessment is carried out. Although relying only on self-report methods can be misleading, for an aware clinician it is still an important source of data on patient's subjective opinion and on the way they experience their symptoms.