Using the population-based data sources in Iceland and the well-characterized AGES-Reykjavik cohort, our overarching aims are on exploring whether pre-diagnostic serum levels of 25-hydroxyvitamin D (25(OH)D) among older individuals living in Iceland were associated with survival after cancer diagnosis. We also wanted to assess the risk of being diagnosed with cancer in association with 25(OH)D levels. In this population living just south of the arctic circle, vitamin D levels largely depend on dietary- and supplemental sources.