<p>As the spleen is a morphologically highly variable organ, radiologists and surgeons frequently encounter normal variants which might be misinterpreted. Accessory spleen is quite a common anatomical variation and generally does not causes any symptoms. However, the finding of an accessory spleen located outside its usual position—the splenic hilum or surrounding. peritoneal folds—is relatively rare in clinical practice and can cause serious diagnostic and/or therapeutic complications: It may mimic a solid tumour or an enlarged lymph. In the review, we summarise the possible anatomical localisations of the accessory spleens (from the thoracic cavity to lesser pelvis and scrotum in males), as well as the diagnostic problems and challenges that the atypical anatomical localisation often causes. We also summarise recent knowledge about the embryological background of accessory spleen formation and address the classification of such a finding—is it a harmless anatomical variation, a developmental defect or a pathological condition of the spleen? According to the recent scientific literature and based the modern imaging techniques, the frequency of accessory spleens is so high that it should be considered rather an anatomical variation than a developmental defect.</p>