Purpose: This study aimed to evaluate the influence of comorbid chronic diseases (CCD) and physical activity (PA) on quality of life (QOL) in lung cancer survivors (LCSs). Methods: The study used a cross-sectional study design. A total of 701 LCSs were recruited from 17 comprehensive cancer rehabilitation clubs in Shanghai, China. Measurements used included the European Organization for Research and Treatment quality of life version 3 questionnaire (EORTC QLQ-C30) and the Functional Assessment of Cancer Therapy -General version 4 questionnaire (FACT-G). Independent variables were CCD and PA. Multiple linear regression models were used to control for the effect of sociodemographic characteristic. Results: Subjects with CCD generally reported lower scores for most EORTC QLQ-C30 and FACT-G scales when compared to subjects without CCD, indicating poorer QOL. Subjects with PA generally reported higher scores for most EORTC QLQ-C30 and FACT-G scales when compared to subjects without PA, indicating better QOL. The influences of five times and more PA per week were larger than the influence of less than five times PA per week. Subjects without CCD and with PA generally reported similar scores for most EORTC QLQ-C30 and FACT-G scales when compared to others without CCD and PA. Subjects with CCD and PA generally reported higher scores for most EORTC QLQ-C30 and FACT-G scales when compared to other LCSs with CCD and without PA. Conclusions: CCD have significantly negative influence on QOL. PA has significantly positive influence on QOL among the LCSs with CCD, not among the other LCSs without CCD.