Diaphragmatic paralysis (DP) after cardiac surgery is an important complication especially in infants. We analyzed the incidence, clinical course, surgical management and follow up of the patients with DP, retrospectively. Between 1996 and 2005, 3,071 patients underwent cardiac surgery. Total number of patients with DP was 152 (4.9%). Out of 152 patients, 42 were surgically treated with transthoracic diaphragm plication (1.3%). The overall incidence of diaphragm paralysis was higher in correction of tetralogy of Fallot (31.5%), Blaloc-Taussig (B-T) shunt (11.1%) and VSD closure with pulmonary artery patch plasty (11.1). The incidence of DP which require plication was higher in B-T shunt (23.8%) arterial switch (19%) and correction of tetralogy of Fallot (11.9%). Mean and median age at the time of surgery were 17.8 +/- 3.6 and 6 months, respectively. Median time from cardiac surgery to surgical plication was 12 days. Indications for plication were repeated reintubations (n = 22), failure to wean from ventilator (n = 12), recurrent lung infections (n = 5) and persistent respiratory distress (n = 3). Mortality rate was 19.1%. Being under 1 year of age, pneumonia and plication 10 days after mechanical ventilation were associated with higher incidence mortality (P < 0.05). Phrenic nerve injury is a serious complication of cardiac surgery. It is more common after some special procedures. Spontaneous recovery is very rare. Being under 1 year of age, plication after 10 days from the surgery and pneumonia are major risk factors for mortality even in plicated patients. Transthoracic plication is helpful if performed early.