Over the past ten years, in oncology there is an increased interest in understanding the cognitive dysfunction caused by chemotherapy also known as chemobrain or chemofog. As a result of oncological therapies the number of survivors of malignant diseases has increased considerably, but the side effects also appear to be more prevalent and severe including persistent cognitive symptoms. Symptoms of chemobrain include memory impairment, loss of concentration, speech and psychomotor deceleration, attention and learning coordination problems, and disturbance of executive functions. The symptoms may be transient but are often long-lasting, the latter negatively affecting functionality and quality of life. Structural and functional imaging studies (MRI, fMRI, PET) and neuropsychological tests are not consistent in the diagnosis of chemobrain. Several factors are suspected leading to the appearance of symptoms, but the specific patomechanism is not yet known. Nutrition status, age, anemia, inflammatory cytokines, stress, and depression can all affect the quality of life and may be related to cognitive symptoms. Currently, there is no treatment strategy for preventing or alleviating cognitive impairement related to chemobrain, and several pharmacotherapies are under investigation. Results imply that understanding the patomechanism of chemobrain can also yield a deeper understanding of cognitive dysfunction associated with depression.