Background: Childhood cancer survivors (CCSs) are at increased risk of developing chronic health conditions, which may be reduced by following a healthy lifestyle including a good diet. Objectives: This study compared the dietary intake and quality of CCSs and the general population. Design: As part of the Swiss Childhood Cancer Survivor Study, we sent a food frequency questionnaire (FFQ) to CCSs who had a median age of 34 years (IQR: 29-40 years) and a median of 26 years (20-31 years) postdiagnosis at the time of survey. We compared dietary intake and quality of CCSs and three comparison groups representing the general adult population using FFQ and 24h recall data (24HDR). We evaluated whether mean individual intake met national dietary recommendations and used the Alternative Healthy Eating Index (AHEI) to estimate diet quality. Results: The 774 CCSs in our study were compared to 8964 participants in the Bus Santé study, 1276 participants in the CoLaus study, and 1134 participants in the Swiss National Nutrition Survey. Dietary intake was equally poor in CCSs and the general Swiss population. CCSs consumed inadequate amounts of vitamin D, fiber, carbohydrates, iron, vitamin A, and calcium (12%, 41%, 72%, 72%, 79%, and 89% of the recommended intakes, respectively), and excessive amounts of saturated fat, protein, cholesterol, and total fat (137%, 126%, 114%, and 107% of the recommended intakes). The mean AHEI score in CCSs was low at 48.0 (men: 45.0, women: 50.9) out of a maximum score of 100. The general population, assessed by 24HDR, scored lower overall than CCSs (41.5; men: 38.7, women: 43.8). Clinical characteristics were not associated with diet quality in CCSs. Conclusion: Long-term CCSs and the general adult population have similarly poor dietary intake and quality in Switzerland, which suggests population-based interventions for everyone.