The purpose of this study was to determine the prevalence of enlarged mesenteric lymph nodes in asymptomatic children. We prospectively studied 189 consecutive asymptomatic children from the outpatients’ nephrological clinics who were referred for abdominal ultrasound. For comparison, we retrospectively reviewed the abdominal CT studies of 99 children, performed following blunt abdominal trauma. The children of both groups were divided into four subgroups according to their ages. The size, the number and the morphology of mesenteric lymph nodes were assessed. On abdominal ultrasound, enlarged mesenteric lymph nodes were detected in 55 of 189 asymptomatic children (29.1%). The longitudinal diameter of the lymph nodes ranged between 5 mm and 19 mm. These lymph nodes were arranged in clusters (three to nine in number in a cluster). All the lymph nodes were oval-shaped, flattened, and without any discomfort following graded transducer compression. On abdominal CT, enlarged mesenteric lymph nodes were diagnosed in 28 of the 99 children (28.3%). These lymph nodes measured more than 5 mm and were arranged in clusters (three or more in number). In seven of these children associated minimal mural thickening of the terminal ileum was seen. The presence of enlarged mesenteric lymph nodes in asymptomatic children of all ages and in both sexes is a common, non-specific finding and should be evaluated only in the appropriated clinical context.