Background The increasingly large sample size requirements of modern adult mental health research suggests the need for a data collection and diagnostic application that can be used across a broad range of clinical and research populations. Aims To develop a data collection and diagnostic application that can be used across a broad range of clinical and research settings. Method We expanded and redeveloped the OPCRIT system into a broadly applicable diagnostic and data-collection package and carried out an interrater reliability study of this new tool. Results OPCRIT+ performed well in an interrater reliability study with relatively inexperienced clinicians, giving a combined, weighted kappa of 0.70 for diagnostic reliability. Conclusions OPCRIT+ showed good overall interrater reliability scores for diagnoses. It is now incorporated in the electronic patient record of the Maudsley and associated hospitals. OPCRIT+ can be downloaded free of charge at http://sgdp.iop.kcl.ac.uk/opcritplus.