OBJECTIVES: To estimate incremental healthcare expenditure associated with comorbid cardiovascular disease (CVD) among patients with chronic obstructive pulmonary disease (COPD) in the hospital setting.  METHODS: Retrospective data derived from the 2007 National Inpatient Sample (NIS) of the Healthcare Cost Utilization Project (HCUP) was analyzed. Hospital inpatient discharge records for patients with a primary diagnosis of COPD and who were ≥40 years of age; were extracted to form the study sample. The sample was then categorized into two groups based on whether there was a secondary diagnosis of CVD. Incremental healthcare expenditure due to comorbid CVD was then determined by comparing hospital charges among the two groups. In addition to hospital charges, national estimates of hospital length of stay (LOS) and in-hospital mortality were also examined and compared between the two groups. For patients with COPD and comorbid CVD, the outcomes were compared across the different CVDs (hypertension, heart failure, ischemic heart disease, pulmonary heart disease, cerebrovascular disease, and cardiomyopathy and dysarrythmia).  RESULTS: Of the 114,812 COPD-related hospital discharges in 2007; 78.23% (n=89,822) had CVD listed as a secondary diagnosis. Mean hospital charges were $15,691(95% CI $14,943 $16,439) for patients with COPD and no comorbid CVD, and were $23,986 (95% CI $23,012.59 $24,959.22) for patients with COPD and CVD. Among COPD patients with comorbid CVD, the mean charges were highest for those with cardiomyopathy and dysarrythmia, at $25,359(95%CI$24,052.96 $26,664.45). The mean LOS was also higher among COPD patients with comorbid CVD as compared to those without comorbid CVD (4.59 days vs. 4.16 days). The mean LOS was also longest for patients with cardiomyopathy and dysarrythmia at 5.75 days.  CONCLUSIONS: Health care expenditure due to comorbid CVD is substantial among hospitalized patients with COPD.