Although childhood tuberculosis has declined dramatically in the UK over the last century, it is now increasing again and globally childhood tuberculosis still accounts for a significant proportion of the tuberculosis disease burden. Children may present with non-specific symptoms, and because of the paucibacillary nature of disease and the difficulty of producing sputum samples, tuberculosis in children is often difficult to diagnose. Apart from the traditional diagnostic methods, like chest X-ray, tuberculin skin testing and mycobacterial staining or culture, new diagnostic strategies have been developed. In particular, immune-based diagnostics, such as interferon-gamma release assays, have now been introduced for clinical use. However these tests do not offer substantial improvements in sensitivity over tuberculin skin testing for the diagnosis of active disease. Further research is needed to develop better diagnostic tests for tuberculosis in children.