Purpose: The purpose of this study was to identify the factors that predict discomfort after coronary angiography or percutaneous coronary intervention (PCI) among hospitalized patients. Methods: A total of 203 patients who underwent coronary angiography or PCI were recruited from C hospital located in S city, J province, from June through August 2008. The level of discomfort was measured and standardized by two instruments, discomfort questionnaire and the Visual Analogue Scale (VAS). Results: Stepwise multiple regression showed that the factors predicting the level of discomfort were type of angiography, gender, previous angiography, dysuria, pre-information, and sleep satisfaction, which together explained 30.6% of the total variance of the level of discomfort. Conclusion: Patients who had previous experience with these procedures, received a pre-information about the upcoming procedure, had no dysuria, and had slept well after the procedure were less likely to complain discomfort. Pre-informed education should be given by nurses to patients who will have an angiography or PCI to reduce their physical and emotional discomforts.