Anthropometry (measurement of body dimensions) has been used for clinical diagnosis of growth and developmental disorders during pregnancy and after birth. Different brain volumes have also been shown in abnormal developmental disorders. This study compares the different horizontal diameters of the left- and right-hand thumbnails and asymmetry of lateral cerebral ventricles in children with developmental delays. This retrospective case control study was carried out in the Pediatric Neurologic Outpatient of a university hospital in Tehran, Iran (2009-2011). Twenty-eight patients with motor developmental disorders (case) and 28 healthy individuals (control) had brain MRIs and volume of lateral cerebral ventricles size had been studied. The maximum horizontal diameters of the left and right thumbnails were measured by calipers during physical and neurological exams by a pediatric neurologist. Finally, we compared and analyzed different horizontal diameters of the left and right hand thumbnails and asymmetry of lateral cerebral ventricles. There was a significant correlation between asymmetry of brain lateral ventricles size and mean difference of horizontal diameter of thumb nails (P = 0.0001). A meaningful relation between brain hemispheres asymmetry and developmentaldelay (P = 0.04) was seen. The asymmetry of thumbnails can be a marker for asymmetry of lateral ventriclesand child developmental delays.