A clicking, crackling, or crunching sound over the cardiac apex, sometimes followed or accompanied by left-sided chest pain, is usually thought to be caused by pericarditis. It is frequently ignored that these symptoms can be due to a small left-sided pneumothorax, called noisy pneumothorax. The pneumothorax can be visualized on X-ray taken in full expiration. Noisy pneumothorax can be followed by various electrocardiographic changes, thus simulating myocardial infarction and other serious heart diseases. Therefore, it is important to have this differential diagnosis in mind as a possibility when healthy, young people are admitted to the hospital with heart symptoms. Two cases of noisy pneumothorax simulating pericarditis are described.