Background: Cancer is a major public health problem all over the world. Monitoring the evolution of the cancer burden in the State of Qatar is of great value but has never been explored in depth. Aims: The aim of the study was to determine the incidence patterns of cancer cases, assess trends during the period 1991-2006 and make comparisons with other countries. Methods: This was a retrospective cohort study based on the Cancer disease registry of Al Amal Cancer hospital, State of Qatar, from 1991-2006. All Qataris and non-Qataris, males and females, who were diagnosed with any type of cancer were included in this study. The diagnostic classification of definite cancer cases was made according to the International Classification of Disease 10th revision (ICD-10). Results: A total of 5,825 cancer cases were registered in Qatar during the period 1991-2006 with 56.7% in males and 43.3% in females, 35.6% in Qataris and 64.4% in non-Qataris. Incidence rates per 100,000 population showed that lung (5.9), lymph node (5.9), bone marrow (4.1) and connective tissue (3.9) were the top major cancers in men. In women, breast (30.1), genital organs (9), lymph node (6.8), rectum (6.1) and thyroid (5.7) cancers were the leading cancers. There was a sharp rise in the total number of cancer cases during the period 2002-2006 of 57.1% compared to the period 1991-1996. The incidence rate of cancer cases increased with increasing age in all cancer types except for breast cancer in women above 65 years old. During the study period, the five most common cancers among women were different from those in men. The incidence rate per 100,000 population of all cancer types in Qatar (63.1) was remarkably lower than the other Middle East countries and the UK. Conclusions: Cancer is an important public health problem in Qatar, with increase in incidence with age. Incidence rates of all cancers were higher across all age groups of women compared to men. Lung cancer was the most frequent cancer diagnosed in men and breast cancer in women. More epidemiological studies are now required to elucidate the patterns of cancer and related risk factors.