We report two pediatric cases with Hirayama disease-a 16-year-old boy with a left wrist drop and a 14-year-old-boy with weakness and muscle atrophy of right hand. Motor nerve conduction study revealed decreased motor nerve action potential amplitudes in the ulnar nerve and radial nerve of the affected hands. The former patient showed normal magnetic resonance imaging (MRI) of the cervical spine, but the latter showed mild, asymmetric thinning of the anterior spinal cord at levels C5 to C7. Following active rehabilitation and avoidance of neck flexion, no further progression of neurological findings was noticed. These clinical findings were typical of Hirayama disease. We show that timely and accurate diagnosis for Hirayama disease is possible with awareness of disease history, careful physical examination, and the use of neurophysiological studies and MRI studies.