Persons with malignant disease have been a neglected population for research in smoking cessation. Besides the well-established role of cigarette smoking in the development of several types of cancers, there are numerous adverse health consequences of continued smoking for the diagnosed cancer patient. These include: increased risk of further neoplasms, poorer survival, and complications of surgery, radiation and chemotherapy; risk of non-neoplastic smoking-related diseases; and additional impairment of appetite and nutrition. Smoking prevalence at diagnosis is highest among patients with smoking-related cancers. Prospective studies of a variety of cancer patient populations are needed to assess patterns of continued smoking and cessation. Systematic quit smoking programs should be integrated into cancer treatment regimens. Currently, two trials testing interventions delivered by medical providers are in progress. Important research issues concerning intervention in cancer patient smoking behavior include: identification of relevant target groups; definition of intervention style and content; delineation of dimensions of treatment; and documentation of beneficial effects. The growing number of long-term cancer survivors and the complications from other smoking-related diseases dictate that the smoking cessation needs of this population be addressed.