Background: This study aimed 1) to assess whether the contribution of chronic conditions to disability varies according to the educational attainment, 2) to disentangle the contributions of the prevalence and of the disabling impact of chronic conditions to educational disparities. Methods: Data of the 2008-09 Disability Health Survey were examined (N = 23,348). The disability indicator was the Global Activity Limitation Indicator (GALI). The attribution method based on an additive hazard model was used to estimate educational differences in disabling impacts and in the contributions of diseases to disability. Counterfactual analyses were used to disentangle the contribution of differences in disease prevalence vs. disabling impact. Results: In men, the main contributors to educational difference in disability prevalence were arthritis (contribution to disability prevalence: 5.7% (95% CI 5.4-6.0) for low-educated vs. 3.3% (3.0-3.9) for high-educated men), spine disorders (back/neck pain, deformity) (3.8% (3.6-4.0) vs. 1.9% (1.8-2.1)), chronic obstructive pulmonary diseases (2.4% (2.3-2.6) vs. 0.6% (0.5-0.7)) and ischemic heart /peripheral artery diseases (4.1% (3.9-4.3) vs. 2.4% (2.2-3.0)). In women, arthritis (9.5% (9.1-9.9) vs. 4.5%, (4.1-5.2)), spine disorders (4.5% (4.3-4.7) vs. 2.1% 1.9-2.3) and psychiatric diseases (3.1% (3.0-3.3) vs. 1.1% (1.0-1.3)) contributed most to education gap in disability. The educational differences were equally explained by differences in the disease prevalence and in their disabling impact. Conclusions: Public health policies aiming to reduce existing socioeconomic disparities in disability should focus on musculoskeletal, pulmonary, psychiatric and ischemic heart diseases, reducing their prevalence as well as their disabling impact in lower socioeconomic groups.