The invention relates to a method which improves the correspondence between the produced fancy yarn and the predetermined configuration of said fancy yarn. According to the inventive method, the fancy yarn is guided through a sensor device in a spinning device after it is formed and the diameter of the fancy yarn is continuously measured by the sensor device. The fancy configuration of the produced yarn is determined on the basis of the measured values of the diameter and is compared with the predetermined fancy configuration. The comparison is carried out until sufficient correspondence between the predetermined fancy configuration and the fancy configuration of the optimized, produced yarn is achieved.