BACKGROUND The small ubiquitin-like modifier 1 (SUMO1) and small ubiquitin-like modifier 1 pseudogene 3 (SUMO1P3) are long noncoding RNAs (lncRNAs). The prognostic significance of SUMO1 and SUMO1P3 expression in non-small cell lung cancer (NSCLC) remains unclear. This study aimed to use clinical, genetic, and survival data from the Cancer Genome Atlas (TCGA), to analyze the prognostic significance of SUMO1 and SUMO1P3 expression in the two main subtypes of NSCLC, lung adenocarcinoma (LUAD) and lung squamous cell carcinoma (LUSC). MATERIAL AND METHODS Data were acquired from TCGA and in silico survival analysis was performed. SUMO1 and SUMO1P3 expression were compared between patients with LUAD and LUSC. Patient outcome was assessed as complete remission (CR), partial remission (PR), stable disease (SD), and progressive disease (PD). Recurrence-free survival (RFS) was defined as the survival time from primary surgery to the time of locoregional or distant recurrence of lung cancer. RESULTS SUMO1P3 was significantly increased in LUSC and LUAD tissues compared with adjacent normal lung tissue and was significantly co-expressed with SUMO1. SUMO1P3 expression was significantly increased in patients with LUAD but not LUSC with reduced RFS after primary or follow-up treatment. Although patients with LUAD who had high SUMO1 or SUMO1P3 expression had reduced RFS compared with low expression groups, univariate and multivariate analysis showed that only SUMO1P3 expression was independently associated reduced RFS (HR, 1.418; 95% CI, 1.041-1.930; p=0.027). CONCLUSIONS SUMO1P3 expression was an independent indicator of reduced RFS in patients with LUAD.