Rationale, aims and objectives: Emergency short-stay unit (SSU) alleviates emergency department (ED) overcrowding, but may affect in-hospital indicators. Cardiology patients comprise a substantial part of patients admitted at SSU. This study evaluated whether SSU opening differentially modified in-hospital indicators at a whole general hospital and at its cardiology division (CARD). Methods: We retrospectively analysed indicators based on 859 686 ED visits, and 171 547 hospital admissions, including 12 110 CARD admissions, from 2007 to 2018 at a general tertiary hospital, and compared global ED indicators and in-hospital indicators at the hospital and CARD before (2007-2011) and after (2011-2018) SSU opening. Results: After SSU opening, monthly ED bed occupancy rate decreased (mean ± SD 200 ± 18% vs 187 ± 22%; P < .001) and in-hospital admissions from ED increased at the hospital (median [interquartile range] 460 [81] vs 524 [41], P < .001) and CARD (50 [12] vs 54 [12], P = .004). In parallel, monthly in-hospital elective admissions decreased at CARD (34 [18] vs 28 [17], P = .019), but not at the hospital (712 [73] vs 700 [104], P = .54). Average length of stay (LOS) increased at both hospital (8.5 ± 0.3 vs 8.7 ± 0.4 days, P < .001) and CARD (9.2 ± 1.5 vs 10.3 ± 2.3 days, P = .002) after SSU opening, but percent admissions at SSU showed a direct relationship with LOS solely at CARD. Furthermore, cardiology patients admitted at SSU had greater LOS, prevalence of coronary heart disease and age than those admitted at the conventional cardiology ward.Conclusions: SSU opening improved ED crowding, but was associated with changes in in-hospital indicators, particularly at CARD, and in the characteristics of hospitalized cardiology patients. These findings suggest that in-hospital cardiology services may need re-evaluation following SSU opening at a general hospital.