Introduction. Vitamin D or "vitamin of the sun" is well known for its anti-inflammatory and immunomodulatory effects, prevention of osteomalacia and osteoporosis and influence on the metabolism of calcium and bones. In addition, it prevents diabetes, multiple sclerosis, cancer, heart disease and even depression. Therefore, studies show that vitamin D, which the human body produces through its exposure to the sun, can reduce the risk of colorectal cancer, breast cancer, ovaries, prostate or any other type of cancer. It also influences many physiological processes, including muscle function, cardiovascular homeostasis, nerve function, cell integrity and immune response. A lot of studies show that this vitamin fights cancer by encouraging cell differentiation, preventing cell growth, inducing apoptosis and preventing the formation of blood vessels within tumors. Following observational studies, it has been noted that the high prevalence of vitamin D deficiency, combined with the discovery of increased risks of certain cancers, suggests that vitamin D lack may account for several thousand annual premature cancer deaths. Aim of the study. The purpose of this study was to present the main conclusions about vitamin D and its effects in cancer prevention and treatment. This finding creates a new impetus for providing suitable vitamin D intake to reduce the risk of cancer. Materials and methods. The review was performed by searching the PubMed database including publications on the etiology and prevention of chronic vitamin D. The most relevant literature was revised from 2010-2019. Results. In vitro and animal studies indicate that vitamin D may have anti-cancer benefits, including against the progression and metastasis of a wide spectrum of cancers. This is because human cells are capable of metabolizing 25-hydroxyvitamin D in 1,25-(OH)-2D, the reaction being catalyzed by enzyme 1-α-hydroxylase (CYP27B1). The combined presence of 25-(OH) D-1 hydroxylase as well as the specific receptor in several tissues introduced the idea of a paracrine role for 1,25-(OH) 2D. Furthermore, it has been shown that 1,25-(OH)-2D promotes cell differentiation and has anti-inflammatory, pro-apoptotic and anti-angiogenic actions, and also inhibits the proliferation of cancer cells. Conclusions. Vitamin D deficiency and insufficiency are closely linked to the increased prevalence of cancer. Thus, vitamin D can be administered within the norm (250-500 nmol/L) to prevent cancer as well as against its progression and metastasis. Therefore, the academic environment, public funding agencies and industry should urgently design appropriate studies in order to define better the causal relationship between vitamin D nutrition and cancer, as well the optimal vitamin D nutrition based on an accurate measurement of 25-(OH)-D, and inform the public and medical profession accordingly.