['To investigate the correlation between p300 (a transcriptional co-activator) expression and clinical/prognostic characteristics in surgically resected NSCLC patients for the purpose of identifying patients with increased risk of cancer recurrence and providing them with tailored therapy.', 'One hundred and sixty-nine completely resected NSCLC patients were included in this study. Paraffin-embedded primary tumour tissues of patients were supplied to produce a tissue microarray, and immunohistochemistry was used for the evaluation of p300 expression. The clinical/prognostic significance of p300 expression was analysed for statistical significance. Survival was calculated by the Kaplan-Meier method, and the log-rank test was used to assess differences in survival between the groups. The prognostic impact of clinicopathologic variables and p300 expression was evaluated using a Cox proportional hazards model.', 'High expression of p300 was associated with poor disease-free survival (p = 0.027) and overall survival (p = 0.006) in NSCLC patients. Further analysis suggested that this difference in overall survival also existed in patients with T2 (p = 0.040), positive lymph nodes (p = 0.023), stage IIIA (p = 0.003), adenocarcinoma (p = 0.021), and a well-differentiated histological grade score (p = 0.011). The multivariate Cox regression analysis showed that low p300 expression is an independent marker of better disease-free survival (relative risk = 0.628, p = 0.047) and overall survival (relative risk = 0.545, p = 0.024) in operable NSCLC patients.'] Does high expression of the transcriptional co-activator p300 predict poor survival in resectable non-small cell lung cancers?