The aim of this study was to investigate and describe the presenting phenotype of children with the 22q11 deletion syndrome and to describe common clinical features that could serve as guidelines in the clinical diagnostic process preceding genetic testing. A hospital-based study of 100 consecutive children and adolescents with 22q11 deletion was initiated. The patients were divided into two groups according to age at diagnosis: before or after 2 years of age. Clinical features were grouped into a core set of eight features: cardiac defects, non-visible/hypoplastic thymus or infection problems, hypocalcaemia, feeding difficulties, cleft palate/speech-language impairment, developmental delay/learning difficulties, characteristic dysmorphic features and other malformations and deformities. The median age at diagnosis was 6.7 years. Of all patients, 26% were diagnosed in infancy and 92% had a congenital cardiac defect, whereas 54% of those diagnosed later had a cardiac defect. A cleft palate was present in 25 cases and 44 had some other malformation or deformity. All presented with a combination of many of the core features. Of those diagnosed after 2 years of age, the majority presented with speech-language impairment, developmental delay or learning difficulties and recurrent infections. Characteristic mild dysmorphic features were noticed in all children. CONCLUSIONS In spite of variable clinical expression, children with 22q11 deletion share a number of major features and have a characteristic phenotype. A high proportion have no cardiac defect and hence a risk of diagnostic delay. Increased awareness and knowledge among general paediatricians and other specialists who meet these children early in life is needed to reduce the diagnostic delay.