Background Routine x rays are not recommended in emergency department (ED) management of common respiratory conditions (croup, bronchiolitis and asthma).

Objectives To describe x ray utilisation for these conditions across all ED in Ontario, Canada (population 13 million) and to test whether hospital resources and settings were associated with variations in utilisation.

Methods We used administrative health records and survey data from all ED (151) in Ontario, Canada. General estimating equations modelled the association of hospital resources (type of staffing, size, teaching status) with x ray use in children aged 3–24 months with croup and bronchiolitis and 1–19 years with asthma who were seen and discharged home from ED from 2004 to 2006.

Results We analysed 9894, 4932 and 35 150 children with croup, bronchiolitis and asthma, respectively. Overall x ray rates were 10%, 43% and 26%. Adjusting for age, sex, co-morbidity and severity of illness, children seen at academic hospitals with frontline paediatric physicians were significantly less likely to have x rays (adjusted odds ratios (AOR) 0.48, 95% CI 0.28 to 0.83 (croup), AOR 0.13 (CI 0.06 to 0.28) (bronchiolitis), AOR 0.12 (CI 0.02 to 0.66) (asthma)) as compared with large community hospitals with paediatric consultants. The highest rates of x ray across all conditions were at teaching hospitals with no paediatric consultants.

Conclusions Significant variability exists in ED x ray utilisation that is not explained by patient factors. Less overutilisation occurs in academic settings with frontline paediatric emergency medicine staff. These hospitals can be used to benchmark x ray rates and describe strategies to reduce overutilisation.