Background: To compare differences in local control rates, overall survival rates and disease-free survival rates for medically inoperable patients, in performance status 0-1 vs. 2, with early non small cell lung cancer (NSCLC) treated with Stereotactic body radiotherapy (SBRT) or conventional radiotherapy (RT) at our centre. Methods: From September, 2005 to December, 2009, 51 medically inoperable patients were treated with SBRT. 3 fractions (F) of 15 Gy. Planned treatment duration was 9 days. 31 medically inoperable patients were treated with conventional RT with 80 Gy/35-40F in the period of February, 1999 through December, 2004. We used 3-D conformal radiotherapy. The prescribed dose was 80 Gy in 35-40F to cover 95% of the PTV. All tumors were histological or cytological proven NSCLC T1-2N0M0. Results: The potential median follow-up time was 28.9 months for the SBRT group vs. 111.3 months in the conventional RT group. The median overall survival (mOS) for patients in PS 0-1 was 39.4 months vs. 30.9 months for SBRT and conventional RT respectively (p = 0.04) and for patients in PS=2 mOS was 25.3 months vs. 8.8 months (p=0.24). Disease free survival rates for patients in PS 0-1 at 1 year and at 3 years were 100% vs. 95.2% and 84.8% vs. 73.6%, SBRT and conventional RT respectively (p = 0.21) and for patients in PS=2 87.8% vs. 64.8% at 1 year and 43.4% vs. 32.4% at 3 years (p=0.30). Local failure free rates at 3 years in were in PS 0-1 group 85.8% vs. in 54.9% PS=2 group (p=0.092). SBRT PS 0-1 local failure free rates of 93.4% vs. 77.1% in the conventional group (p=0.21). For PS=2 66.5% vs. 50%, SBRT vs. conventional RT (p=0.85). In a Cox analysis only female gender and PS 0-1 were significant factors while stereotactic treatment was of borderline significance (p=0.056). Conclusions: SBRT offers excellent local control and survival superior to high-dose conventional RT in patients with good PS. SBRT is a cost-effective treatment and is the more convenient treatment for the patients.