Cigars, while containing many of the same carcinogens as cigarettes, has a lower overal risk of lung cancer than cigarettes.
Dr C. Evertt Koop, former Surgeon General for the US has been quoted as stating that occassional cigar smoking is to be considered of minimal health risk unless you have special or hereditary factors that would place you in a higher risk for tobacco-related illnesses. In fact research from the National Cancer Institutes indicates that the health risk posed by both cigars and cigarettes are strongly linked to frequency of use.
The key to the claim that cigars are less dangerous than cigarettes lies mainly in the way that people smoke them. Cigarette smokers, for the most part, are addicted to the substance and the actions associated with smoking while cigar smokers, for the most part, are irregular smokers that enjoy a fine stick every now and again. Since you are not inhaling cigar smoke like one would cigarette smoke, it becomes inheritly less likely to contract lung cancer.