Personality refers to an individual's enduring and pervasive personal motivation, emotion, interpersonal style, attitudes and behavior that are stable over a long time after young adulthood. In relation to the cancer trajectory, three basic and one other personality traits have been studied with some frequency, namely neuroticism, extraversion, conscientiousness and optimism. The considerable stability of personality over time makes it a potential long-acting etiological factor for the development of cancer. However, the studies performed so far do not give much support to personality as a causative factor for cancer. Some studies of cancer survival have found significant associations between lower optimism and higher neuroticism with shorter survival. More mental distress and fatigue and poorer quality of life is significantly associated with higher neuroticism and lower optimism at cancer screening, diagnosis and primary treatment, short- and long-term follow-up and towards the end of life. Neuroticism is a strong predictor of post-traumatic stress disorder triggered by cancer as a life-threatening experience eventually leading to negative personality changes. To what extent cancer leads to positive personality changes (post-traumatic growth) is currently unsettled. Basic personality traits are strongly associated with lifestyle, which is considered an important etiological factor for the development of cancer. The methodological problems in the study of personality and cancer are considerable, and many research designs used so far may have been too simplistic. Studies of potential biomarkers for personality traits combined with inflammation markers of cellular carcinogenesis in longitudinal designs could be promising for the future. High neuroticism is important for the clinical management of cancer patients and should gain more attention from oncologists in the future.