Objective This study probes into site-specific cancer mortality inequalities by employment and occupational group among Belgians, adjusted for other indicators of socioeconomic (SE) position. Design This cohort study is based on record linkage between the Belgian censuses of 1991 and 2001 and register data on emigration and mortality for 01/10/2001 to 31/12/2011. Setting Belgium. Participants The study population contains all Belgians within the economically active age (25–65 years) at the census of 1991. Outcome measures Both absolute and relative measures were calculated. First, age-standardised mortality rates have been calculated, directly standardised to the Belgian population. Second, mortality rate ratios were calculated using Poisson’s regression, adjusted for education, housing conditions, attained age, region and migrant background. Results This study highlights inequalities in site-specific cancer mortality, both related to being employed or not and to the occupational group of the employed population. Unemployed men and women show consistently higher overall and site-specific cancer mortality compared with the employed group. Also within the employed group, inequalities are observed by occupational group. Generally manual workers and service and sales workers have higher site-specific cancer mortality rates compared with white-collar workers and agricultural and fishery workers. These inequalities are manifest for almost all preventable cancer sites, especially those cancer sites related to alcohol and smoking such as cancers of the lung, oesophagus and head and neck. Overall, occupational inequalities were less pronounced among women compared with men. Conclusions Important SE inequalities in site-specific cancer mortality were observed by employment and occupational group. Ensuring financial security for the unemployed is a key issue in this regard. Future studies could also take a look at other working regimes, for instance temporary employment or part-time employment and their relation to health.