The aim of this work is to identify the association between tooth agenesis and systemic pathologies in paediatric patients. The Authors used clinical case-history and orthopanoramic rx of paediatric patients between 5 and 12 years old, gone to U.O.C. of Paediatric Dentistry, from genuary 2006 to genuary 2009. It resulted that 9.1% of 1190 children presented tooth agenesis and in this group the Authors put in evidence a percentage of 41.5% with syndromes or orofacial diseases.