Denial in cancer patients is a well-known concept. The definition of denial, however, is not unequivocal and covers different ways of evading painful events or feelings. This thesis studies denial and its relation to the quality of life in lung cancer patients. To assess the level of denial the ‘Denial of Cancer Interview’ (DCI) was developed. Denial was measured at different time points in the course of the disease. The key-finding from this study is that patients fare better when they express a moderate level of denial or increase their level of denial from the moment of diagnosis over time. This study shows convincingly that denial in lung cancer patients deserves attention in clinical practice. In this era of self-disclosure it is good to realize that some patients need protection against unbearable facts and feelings. Denial can serve this need and should be respected.