Observational research is important for understanding the real-world benefits of advancements in lung cancer care. Integrated health care systems, such as Kaiser Permanente Northern California, have extensive electronic health records suitable for such research, but the generalizability of their populations is often questioned.Leveraging data from the California Cancer Registry, the authors compared distributions of demographic and clinical characteristics, in addition to neighborhood and environmental conditions, between patients diagnosed with lung cancer from 2015 through 2019 at Kaiser Permanente Northern California, National Cancer Institute-designated cancer centers (NCICCs), and all other non-NCICC hospitals within the same catchment area.Of 20,178 included patients, 30% were from Kaiser Permanente Northern California, 8% from NCICCs, and 62% from other non-NCICC hospitals. Compared to NCICC patients, Kaiser Permanente Northern California patients were more similar to other non-NCICC patients on most characteristics. Compared to other non-NCICC patients, Kaiser Permanente Northern California patients were slightly older, more likely to be female, and less likely to be Hispanic or Asian/Pacific Islander and to reside in lower socioeconomic status (SES) neighborhoods. In contrast, NCICC patients were younger, less likely to be female or from non-Asian/Pacific Islander minoritized racial groups, and more likely to present with early-stage disease and adenocarcinoma and to reside in neighborhoods with higher SES and lower air pollution than Kaiser Permanente Northern California or other non-NCICC patients.Patients from Kaiser Permanente Northern California, compared to NCICCs, are more broadly representative of the underlying patient population with lung cancer.Research using electronic health record data from integrated health care systems can contribute generalizable real-world evidence to benchmark and improve lung cancer care.