BAC is a common pattern in conventional lung adenocarcinoma. In the past, however, there were no well-defined criteria for BAC. As a result, it was difficult to evaluate the prognosis on this type of lung adenocarcinoma. Though the 1999 WHO classification of BAC provides a useful framework, it does not provide detailed enough information to predict prognosis in lung adenocarcinomas with BAC feature. The aim of this study was to address the prognostic value of bronchioloalveolar carcinoma (BAC) component in lung adenocarcinoma. Ninety-one consecutive surgically treated patients with adenocarcinoma exhibiting various degrees of BAC features and complete follow-up records were retrospectively studied. According to the percentage of BAC component designed as less than 50%, 50%-79%, 80%-99%, and 100%, tumors were classified as type I, type II, type III, and type IV respectively. The overall 5-year survival rate was 64.84%. Multivariate analysis revealed that the four classified types are independent prognostic factors (P=0.0008), as is tumor stage (P=0.0000). The 5-year survival rates were 39.29%, 58.82%, 81.25%, 85.71% for the four classified types respectively, and were 88.89% for stage I, 46.15% for stage II, and 23.81% for stage III. However, the size of tumor (>2 cm) was significant only in the univariate analysis (P=0.0275). In the patients with tumor size exceeding 2 cm in diameter, the BAC component was also significant to predict prognosis (p=0.0008). In lung adenocarcinoma, the BAC component may prove to be useful to predict the outcome of the patients, and the percentage of BAC pattern and pathological stage appear to be two independent prognostic factors.