The SMN1 and NAIP genes are related to the development of spinal muscular atrophy (SMA), which is characterized by degeneration of motor neurons leading to progressive muscular weakness and atrophy. The SMN1 gene is homozygously deleted in most SMA patients, and now recognized as a responsible gene for SMA. The NAIP gene is often deleted in the SMA patients with the severest form of SMA, and now considered to be a modifying factor of the severity of SMA. Our previous study of five Vietnamese SMA patients showed that the SMN1 gene deletion was detected in one patient, although the NAIP gene deletion was not detected in any patients. In this study, we analyzed 12 Vietnamese SMA patients who were not enrolled in the previous study. The SMN1 gene was homozygously deleted in six out of 12 patients, and the NAIP gene deletion was detected in five patients. Taken together with our previous data, the SMN1 gene deletion was detected in seven out of 17 Vietnamese SMA patients and the NAIP gene deletion in five out of 17 Vietnamese SMA patients. These studies suggest that the SMN1 and NAIP gene deletions are not rare in Vietnamese SMA patients. Thus, the confirmation of SMA-related gene deletion will also be a useful tool for the diagnosis of SMA in Vietnam.