OBJECTIVE: To examine the associations between mental and physical illness in hospitalized children. METHODS: The data for this analysis came from the 2009 Kids’ Inpatient Database (KID). Any child with an International Classification of Diseases, Ninth Revision code indicative of depressive, anxiety, or bipolar disorders or a diagnosis of sickle cell disease, diabetes mellitus type 1 or 2, asthma, or attention-deficit/hyperactivity disorder (ADHD) were included. Using SAS software, we performed χ2 tests and multivariable logistic regression to determine degrees of association. RESULTS: Children discharged with sickle cell disease, asthma, diabetes mellitus type 1, diabetes mellitus type 2, and ADHD were 0.94, 2.76, 3.50, 6.37, and 38.39 times more likely to have a comorbid anxiety, depression, or bipolar disorder diagnosis than other hospitalized children, respectively. CONCLUSIONS: Children with several chronic physical illnesses (asthma, diabetes mellitus type 1, diabetes mellitus type 2) and mental illnesses (ADHD) have higher odds of being discharged from the hospital with a comorbid mood or anxiety disorder compared with other children discharged from the hospital. It is therefore important to screen children hospitalized with chronic medical conditions for comorbid mental illness to ensure optimal clinical care, to improve overall health and long-term outcomes for these children.