The survival of non-Hodgkin lymphoma patients strongly depends on a range of prognostic factors. This registry-based clinical cohort study investigates the relation between socioeconomic position and prognostic markers in 6234 persons included in a national clinical database in 2000-2008, Denmark. Several measures of individual socioeconomic position were achieved from Statistics Denmark. The risk of being diagnosed with advanced disease, as expressed by the six prognostic markers (Ann Arbor stage III or IV, more than one extranodal lesion, elevated serum lactate dehydrogenase (LDH), performance status of two or more, presence of B symptoms and International Prognostic Index (IPI) of two or more), increased with decreasing level of education, in patients living alone, and in men. For instance, a significant decrease in the odds of being diagnosed with elevated LDH (p = 0.02), high performance status (p = 0.004), high IPI score (p = 0.004) and B symptoms (p = 0.02) was seen with higher level of education, whereas high stage of disease was significantly less likely in the higher educated (odds ratio [OR] = 0.85 (0.74-0.99)). The difference in risk seemed not to be mediated by differences in histological subgroups reflecting aggressiveness of disease among the social groups. One of the most likely mechanisms of the social difference is longer delay in those with low socioeconomic position. The findings of social inequality in prognostic markers in non-Hodgkin lymphoma (NHL) patients could already be implemented in the clinical practice if general practitioners (GP's) and physicians on hospitals paid special attention to patients with low educational level and unspecific symptoms.