Positive psychology research studies have lead to greater consideration and promotion of optimal functioning in the different fields of psychology. This article introduces an epistemological questioning about optimal functioning assessment and practical considerations on the use of existing psychopathology scales which can be reinterpreted in order to assess well-being and positive characteristics (if one considers human psychology as a continuum going from disorders to optimal functioning), and the use of existing questionnaires measuring specific positive personality traits (if one considers that the continuum theory may not explain all the phenomena observed). The authors present a selection of questionnaires validated in French, which can be used for research studies and clinical practice.