Objective: Respiratory failure is a major complication after cardiac surgery. The purpose was to evaluate the impact of minimally invasive aortic valve replacement (mini AVR) on the occurrence of left lower lobe atelectasis (LLLA) in the cardiac intensive care unit (ICU). Patients and Methods: 98 patients were scheduled to undergo mini AVR. 14 of these patients were converted to a full sternotomy due to technical problems. These patients were compared to a group of 50 patients having planned AVR through a full sternotomy. The incidence of LLLA was evaluated on the first postoperative chest X-ray in the cardiac ICU. Results: In the group having completed mini AVR 20/84 (24%) had a partial LLLA while in the group having extension to a full sternotomy 9/14 (64%) had LLLA lobe (P<0.005). In the group of 50 patients who had AVR through a full sternotomy, 27 patients (54%) had LLLA in the ICU which is also significantly higher (P<0.008) than the percentage of atelectasis in the mini AVR group. Conclusions: Patients who had mini AVR had a significantly lower incidence of LLLA in the cardiac ICU than patients who had AVR through a full sternotomy.