Purpose: To explore the short-term efficacy and safety of CT-guided microwave ablation (MWA) for treating liver tumors near the diaphragm. Results: The complete response (CR) rate for CT-guided MWA through the lung was 94.7% (124/131). The incomplete response (ICR) rate was 5.3% (7/131), of which 6 patients with ICRs achieved CRs after MWA. The CR rate for Group I was higher than Group H (99.0% vs. 80.0%, P=0.001).The mean follow-up time was 11.2 +/- 7.50 months. The total local recurrence (LR) rate was 15.3% (20/131). The complication rate was 26.5%, and no severe complications were recorded. All complications were controllable and treatable. The incidence of diaphragmatic thickening during the MWA was 18.8% (P>0.05); the incidence of exudative changes inside the lungs was 6.8% (P>0.05). Conclusions: CT-guided MWA can detect changes in liver tissue, in the diaphragm and nearby lung tissues during the ablation process. It's safe and effective to treat tumors close to the diaphragm by CT-guided MWA through the lung. Methods: CT-guided MWA was used on 131 tumors that were close to the diaphragm (distance between tumor and diaphragm 5 5 mm) in 117 patients with liver cancer. The tumors were divided into a < 3.0 cm group (Group I, n= 101) and a 3.0 cm group (Group II, n= 30) based on tumor diameters. The complications within 2 weeks following treatment were counted, and the safety and short-term efficacy of MWA were analyzed.