A B S T R A C TBackground: It is unknown whether a socio-economic difference exists in the association of diet quality with type 2 diabetes incidence, nor how diet influences the socioeconomic inequality in diabetes burden. Methods: In 91,025 participants of the population-based Lifelines Cohort (aged 30, no diabetes or cardiovascular diseases at baseline), type 2 diabetes incidence was based on self-report, fasting glucose 7¢0 mmol/l and/or HbA1c 6¢5%. The evidence-based Lifelines Diet Score was calculated with data of a 110-item food frequency questionnaire. Socio-economic status (SES) was defined by educational level. Cox proportional hazards models were adjusted for age, gender, smoking, energy intake, alcohol intake and physical activity. Findings: In 279,796 person-years of follow-up, 1045 diabetes cases were identified. Incidence rate was 5¢7, 3¢2 and 2¢4 cases/1000 person-years in low, middle and high SES, respectively. Diet was associated with greater diabetes risk (HR(95%CI) in Q1 (poor diet quality) vs. Q5 (high diet quality) = 2¢11 (1¢70À2¢62)). SES was a moderator of the association(p INTERACTION = 0¢038). HRs for Q1 vs. Q5 were 1¢66 (1¢22À2¢.27) in low, 2¢76 (1¢86À4¢08) in middle and 2¢46 (1¢53À3¢97) in high SES. With population attributable fractions of 14¢8%, 40¢1% and 37¢3%, the expected number of cases/1000 person-years preventable by diet quality improvement was 0¢85 in low, 1¢28 in middle and 0¢90 in high SES.Interpretation: Diet quality improvement can potentially prevent one in three cases of type 2 diabetes, but because of a smaller impact in low SES, it will not narrow the socioeconomic health gap in diabetes burden. Funding: None.