Global assessment of functioning represents an important aspect of assessment in clinical practice and research. It can help identify persons in need of psychiatric treatment, have predictive value and measure change over time, including treatment effects. This review examines publications concerning development, psychometric properties and usefulness of three scales for children: Axis-VI in ICD-10 Global Assessment of Psychosocial Disability (GAPD), Children's Global Assessment Scale (CGAS) and Axis-V in DSM-IV Global Assessment of Functioning Scale (GAF). It is based on literature searches in PubMed and PsycInfo (1977-2003), and screening of Scandinavian and English textbooks on child psychiatry. The three scales differ in theoretical guidelines, descriptions of codes/anchor points and psychometric aspects. CGAS has been evaluated in 69 papers and 33 have been published on GAF used for children. The one paper comparing GAPD and CGAS found both scales sufficiently reliable for clinical practice. Reliability of CGAS and GAF has been found to vary from fair to substantial, depending on raters, training and diagnostic groups. International consensus for the use of one scale for global assessment of functioning for children 4-18 years would improve reliability in clinical practice and ease comparisons of studies across countries. A training programme would assist in this.