INTRODUCTION: Although chemoradiotherapy for locally advanced lung cancer has the potential for cure, treatment is avoided in patients with interstitial lung disease because of the risk for severe radiation pneumonitis. Interstitial lung abnormalities (ILA) can be evaluated using high-resolution computed tomography (HRCT) to assess interstitial changes. In this study, we retrospectively examined the feasibility and efficacy of chemoradiotherapy for locally advanced lung cancer patients with ILA. METHODS: Patients who underwent chemoradiotherapy for locally advanced lung cancer at Okayama University Hospital between 2012 and 2015 were reviewed retrospectively. HRCT prior to treatment was evaluated by one pulmonologist and two radiologists using a sequential reading method. RESULTS: Of the 77 patients enrolled in this study, ILA was present in 25 (32.5%) and indeterminate ILA in 24 patients; 28 patients did not have ILA. Desaturation at rest (SpO2 < 95%) and honeycombing on HRCT were not observed in ILA patients. Only one patient with ILA had a low vital capacity (%VC < 80%). Severe radiation pneumonitis (≥Grade 2) occurred in 36.0% of the patients with ILA, but it was controllable; Grade 4 or 5 was not observed. Multivariate analysis showed that >25% of the lung volume receiving >20 Gy was risk factors of severe radiation pneumonitis, but ILA was not. The 2-year survival rates of patients with and without ILA were 56.8% and 74.1%, respectively, but the difference was not significant (P = 0.33). CONCLUSIONS: Chemoradiotherapy was feasible and effective in some patient population with ILA without desaturation, low VC and honeycombing on HRCT.