Introduction: Diabetes mellitus is a group of metabolic disorders characterized by hyperglycemia and accompanied by long term damage, dysfunction and failure of various organs. Aim of the study: to identify the etiology, risk factors and the most common clinical features of newly diagnosed diabetes in children and adolescents. And identification of the factors related to delayed diagnosis or mismanagement in these children. Methods: Ninety nine children (52 males and 47 females) , aged from few days to 13 years, diagnosed with newly diagnosed diabetes, referred and managed at DEMPU in Children’s Hospital, Cairo University. Results: Classic symptoms (polyuria, polydipsia and weight loss) were the most common symptoms (95.9% &90.7%) preceding the diagnosis; and diabetic ketoacidosis was present in 51.5%. Delayed and missed diagnosis was recorded in 49.5 %, with no significant relation to age, district of accommodation or family history of diabetes. Cow’s milk feeding was more frequent, being recorded in 79.3% vs. 20.7% with exclusive breast feeding, and positive family history of diabetes was recorded in 77.3%. Severity at presentation showed no significant relation to age, type of feeding, family history of diabetes or C-peptide level. Conclusion: the classic triad of diabetes is the commonest presenting symptom of diabetes in children. Misdiagnosis and mismanagement are common and accounts for more severe presentation among newly diagnosed diabetic children, with infants below 2 years of age being the most vulnerable group to such problem. Positive family history of diabetes is high and positive FH of type 2 diabetes mellitus is more frequent than type 1or both. Early introduction of cow’s milk appears to be a risk factor for the development of type 1 diabetes mellitus (T1DM).