We examined the correlation between computed tomography (CT) findings and the incidence of epidermal growth factor receptor (EGFR) and KRAS mutations in lung adenocarcinoma. We analyzed the tumors of 136 patients with surgically resected primary lung adenocarcinoma. CT scans were evaluated for the presence of ground grass opacity (GGO), spiculation and the maximum diameter of the tumor was measured. SMart Amplification Process (ver. 2) was used to detect the presence of EGFR and KRAS mutations. EGFR and KRAS mutations were found in 56 (41.1%) and 25 (18.4%) of the 136 cases, respectively. Although no significant association was found between GGO and EGFR mutations (p=0.07), the EGFR mutation occurred more frequently in male patients with GGO than in those without GGO (p=0.04). The KRAS mutation occurred more frequently in patients whose tumor diameter was ≥ 31 mm than in those whose tumor diameter was <30 mm (p=0.003). Evaluation of CT findings may be helpful for determining the presence of EGFR and KRAS mutations, particularly when it is not possible to obtain a tumor specimen.