Olfactory disorders are common and have consequences for the quality of life of patients. The main causes are post viral upper respiratory tract infections, head trauma and sinonasal disease. However, there are many more less frequent causes which we illustrate by showing three different rare cases. A distinguishment between qualitative and quantitative olfactory disorders is made which is mainly based on the patient's history and olfactory testing. It is important to diagnose the cause of an olfactory disorder because treatment options are dependent on it and it can be a symptom of a progressive disease. Olfactory training is a proven treatment for many perceptive olfactory disorders and is easily performed by most patients.