Promotion of good mental health in young people with and without mental disorders has received little empirical research attention and interventions for improving mental health in young people are not well established. This situation could be explained among other reasons due to the difficulties to define and operationalise what good mental health is. The current manuscript, produced by the European College of Neuropsychopharmacology Thematic Working Group on the Prevention of Mental Disorders and Mental Health Promotion (ECNP TWG PMD-MHP), presents a critical review of the available operationalizations for good mental health. A pragmatic conceptual operationalisation of good mental health is a much-needed step towards more standardised research in this field. Good mental health can be defined as a state of well-being that allows individuals to cope with the normal stresses of life and function productively. Universal and selective interventions are suitable to promote mental health. Core domains that define good mental health encompass: (i) mental health literacy, (ii) attitude towards mental disorders, (iii) self-perceptions and values, (iv) cognitive skills, (v) academic/ occupational performance, (vi) emotions, (vii) behaviours, (viii) self-management strategies, (ix) social skills, (x) family and significant relationships (xi) physical health, (xii) sexual health, (xiii) meaning of life, (xiv) and quality of life. These domains should be widely traceable in the literature and can be used to conduct further empirical research in the field of good mental health. Such data can lead to more robust evidence to identify and establish the pathways to follow in order to improve mental health.