Mycoplasma pneumoniae (MP) is, considered to affect rarely children less than 5 yrs of age. This study was performed to describe the epidemiology and the clinical features of MP lower respiratory tract infection (LRTI) in children, presenting to a tertiary children hospital. Eleven month-longitudinal study of LRTI due to MP, diagnosed by polymerase chain reaction (PCR) on throat swab specimen, was performed. Out of 866 children with LRTI admitted to the Gaslini Pediatric Institute in Genoa, 102 had a positive PCR for MP. We found 39 preschool-aged children, 42 school-aged children and 21 young adolescent [6.20 (3.81) yrs old]. Interestingly, eight MP+ infants had <8 months of age. The commonest presentations were cough and/or fever (76.5%). Tachypnoea, upper respiratory tract involvement, diarrhoea and vomiting were more common in the <5 yr Gr as compared to the other groups. Chest X-ray was found abnormal in 76 children: consolidations were the commonest finding. Laboratory test showed that the preschool-aged children had a higher number of lymphocytes (p<0.0001) and monocytes (p=0.009). Thrombocytosis was found in 35.7% of children and was more frequent in the preschool-aged children (p=0.013). MP infection is common in preschool-aged children, including young infants, and may have different clinical presentation, as compared to older children.