Pectus excavatum (PE) is a ventral chest wall deformity, also known as funnel chest, sunken chest, chondrosternal depression or koilosternia. The 4 months old, 1.3 kg intact-female Pekingese dog was evaluated for acute semicoma and convulsion. The client reported that this patient have had chronic loss of appetite, intermittent dyspnea and palpable sunken breast. The other littermates did not show any abnormalities. On physical examination, cachexia (BCS 1/5), concave sternum, flatten thoracic cavity and cardiac murmur were observed. On radiographic study, the caudal sternum cave to vertebrae and narrowing thoracic cavity. The severities of thoracic deformity were evaluated by deformation indices such as-Frontosagittal index (FSI) and vertebral index (VI). Moderate to severe PE was founded by the radiological measurements.