Background: Guideline adherence remains a challenge in clinical practice, despite guidelines' ascribed potential to improve patient outcomes. We studied the level of adherence to recommendations from Dutch national cancer treatment guidelines, and the influence of general and cancer-specific guideline characteristics on adherence. Methods: Based on data from a national cancer registry, adherence was evaluated for 15 treatment recommendations for breast, colorectal, prostate and lung cancer, and melanoma. Recommendations were selected by representatives of the medical specialist associations responsible for developing and implementing the guidelines. We used multivariable multilevel analysis to calculate mean adherence and variation between individual hospitals. Results: Mean adherence to the different treatment recommendations ranged from 40 to 99%. Adherence differed only slightly between older and newer guidelines and between recommendations with low, moderate or high levels of evidence (range 79-84% and 77-91%, respectively), while adherence differed more between recommendations for different cancer types (range 54-99%), different treatment modalities (adherence ranged from 40 to 92%) or recommendations that advised against or recommended in favour of particular treatment (adherence ranged from 75 to 98%). Conclusion: We found significant variation in adherence between different cancer treatment guidelines. While some guideline characteristics that seem to explain this variation may be considered difficult to modify, the potential for variance across cancer types and treatment modalities suggests that adherence could be further improved. At the same time, these results warrant tailored strategies for the improvement of adherence to clinical practice guidelines.