Attending physicians are only required to provide in-hospital coverage during daytime hours in many pediatric intensive care units. An in-hospital 24-hr pediatric intensive care unit attending coverage model has been increasingly popular, but the impact of 24-hr, in-hospital attending coverage on care processes and outcomes has not been reported. We compared processes of care and outcomes before and after the implementation of a 24-hr in-hospital pediatric intensive care unit attending physician model. Retrospective comparison of before and after cohorts. A single large, academic tertiary medical/surgical pediatric intensive care unit. : Pediatric intensive care unit admissions in 2000-2006. Transition to 24-hr from 12-hr in-hospital pediatric critical care attending physician coverage model in January 2004. A total of 18,702 patients were admitted to intensive care unit: 8,520 in 24 hrs; 10,182 in 12 hrs. Duration of mechanical ventilation was lower (median 33 hrs [interquartile range 12-88] vs. 48 hrs [interquartile range 16-133], adjusted reduction of 35% [95% confidence interval 25%-44%], p < .001) and intensive care unit length of stay was shorter (median 2 days [interquartile range 1-4] vs. 2 days [interquartile range 1-5], adjusted p < .001) for 24 hr vs. 12 hr coverage. The reduction in mechanical ventilation hours was similar when noninvasive, mechanical ventilation was included in ventilation hours (median 42 hrs vs. 56 hrs, adjusted reduction in ventilation hours: 33% [95% confidence interval 20-45], p < .001). Intensive care unit mortality was not significantly different (2.2% vs. 2.5%, adjusted p =.23). These associations were consistent across daytime and nighttime admissions, weekend and weekday admissions, and among subgroups with higher Pediatric Risk of Mortality III scores, postsurgical patients, and histories of previous intensive care unit admission. Implementation of 24-hr in-hospital pediatric critical care attending coverage was associated with shorter duration of mechanical ventilation and shorter length of intensive care unit stay. After accounting for potential confounders, this finding was consistent across a broad spectrum of critically ill children.