Diaphragmatic paresis/paralysis can be unilateral or bilateral. Its manifestations range from completely asymptomatically to global respiratory failure. Respiratory functional tests will reveal lowered respiratory pressures with a restrictive syndrome, and a decrease in vital capacity when lying in the supine position compared to sitting. Unilateral paresis is most often self-limited and mainly post-surgical. The bilateral dysfunction, observed in neuromuscular diseases, is often permanent. The treatment consists in the management of specific causes, the optimization of the treatment of comorbidities, and in some cases, diaphragmatic plication, ventilatory support or pacing of phrenic nerves.