Background: Research on ethnic and socioeconomic treatment differences following in-hospital cardiac arrest (IHCA) largely draws on register data. Due to the correlational nature of such data, it cannot be concluded whether detected differences reflect treatment bias/discrimination - whereby otherwise identical patients are treated differently solely due to sociodemographic factors. To be able to establish discrimination, experimental research is needed. Objective: The primary aim of this experimental study was to examine whether simulated IHCA patients receive different treatment recommendations based on ethnicity and socioeconomic status (SES), holding all other factors (e.g., health status) constant. Another aim was to examine health care professionals (HCP) stereotypical beliefs about these groups. Methods: HCP (N = 235) working in acute care made anonymous treatment recommendations while reading IHCA clinical vignettes wherein the patients ethnicity (Swedish vs. Middle Eastern) and SES had been manipulated. Afterwards they estimated to what extent hospital staff associate these patient groups with certain traits (stereotypes). Results: No significant differences in treatment recommendations for Swedish versus Middle Eastern or high versus low SES patients were found. Reported stereotypes about Middle Eastern patients were uniformly negative. SES-related stereotypes, however, were mixed. High SES patients were believed to be more competent (e.g., respected), but less warm (e.g., friendly) than low SES patients. Conclusions: Swedish HCP do not seem to discriminate against patients with Middle Eastern or low SES backgrounds when recommending treatment for simulated IHCA cases, despite the existence of negative stereotypes about these groups. Implications for health care equality and quality are discussed.