Pulmonary embolism is a serious disease that remains unrecognized in up to 70 % of cases during a patienťs life. We present three cases diagnosed in the Pneumology out-patient clinic in one year. These cases serve to illustrate both the main symptoms of pulmonary embolism and also the pitfalls of its diagnosis. It is hardest to distinguish between PE and inflammatory lung diseases (pneumonia, pleuropneumonia). In every case of dyspnoea, which is the main symptom of PE, particularly if it is associated with another symptom (chest pain, hemoptysis) and/or a risk factor (mainly hypercoagulable states, women receiving oral contraceptive or hormone replacement therapy), a diagnosis of PE must be considered and thoroughly excluded or confirmed.

        Key words: pulmonary embolism, deep vein thrombosis