Electronic health (eHealth) sources have great potential to improve patients' access to health information for self-management of secondary prevention after percutaneous coronary intervention (PCI). It remains unclear, however, whether patients are health-related digitally active and whether they have sufficient eHealth literacy. This study aimed to determine the extent to which patients after PCI are health-related digitally active at baseline, 2 and 6 months after PCI, and to determine the association between patients' eHealth literacy and their health-related digital activity.