A Consensus Conference on Specific Learning Disorders has been promoted by the Italian National Institute of Health (Istituto Superiore di Sanità, ISS). The Consensus Conference consisted in a systematic review of the international literature addressing the issues of diagnosis, risk factors and prognosis, treatment, service delivery and organizational models for Specific Learning Disorders (reading, spelling/writing, calculation). Selected papers were examined by a group of Evaluators and then discussed by a Scientific and Technical Committee, whose conclusions were examined and approved by a Jury Panel. The part on diagnostic issues is presented here, encompassing a systematic discussion of the use and appropriateness of diagnostic criteria, parameters, tasks and psychometric indexes as illustrated in the literature, and providing recommendations for clinical practice. Special attention has been devoted to the collection, analysis and discussion of published data concerning languages with transparent orthography. Controversial issues such as discrepancy criteria, role of reading comprehension and importance of accuracy and fluency are discussed.