© Author(s) (or their employer(s)) 2018. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ. Objective Various studies find that the share of emergencies in hospital admissions is higher in deprived areas, but both the explanation and policy implications are unclear. We estimate the extent to which this finding is due to a different disease mix in deprived areas, rather than other explanations such as patient behaviour and general practitioner effectiveness. Design Secondary analysis using English Hospital Episode Statistics data, with disease for elective and emergency admissions in 2008/2009 coded at 186 blocks or 1230 categories and aggregated to lower layer super output area of residence. It is then linked to an appropriate measure of deprivation. Outcome measures The difference in the share of emergencies in hospital admissions between communities in the highest and lowest deciles of deprivation; and the percentage of this difference that is explained if areas in the least deprived decile have the same disease mix as those in the most deprived decile. Results Using the finest disease classification scheme (1230 categories), 71% of the higher share of admissions that were emergencies in decile 1 areas relative to decile 10, is explained by the "adverse" case mix (CM) in deprived areas. The remainder reflects the higher relative use of emergency care in deprived areas for the same conditions. Higher incidence of respiratory and circulatory diseases in deprived areas explains about 30% of the CM contribution. Diseases of the digestive system and abdomen have a high relative use of emergency care in deprived areas. Conclusions The higher use of emergency care in deprived areas is primarily a symptom of the higher prevalence of diseases which have high national rates of emergency to elective care - especially respiratory diseases - rather than an indication of less effective primary care. Nevertheless, there is a higher share of emergency care in admissions in deprived areas for several diseases, most notably of the digestive system.