Ultrasonography, like any imaging method, entails the risk of errors. From among all means of imaging, it is the most subjective and dependent on the examiner’s knowledge and experience. This paper presents the causes of examiner-dependent errors as well as those which result from technical settings and preparation of the patient for the examination. Moreover, the authors discuss the most frequent errors in the diagnosis of splenic conditions, which result from insufficient knowledge concerning anatomical variants of this organ, wrong measurements and incorrect examination technique. The mistakes made in the differentiation of focal lesions of the spleen and its hilum are also discussed. Additionally, the differentiation of collateral circulation, lymph nodes and accessory spleens is mentioned. The authors also draw attention to erroneous interpretation of the left liver lobe as a fragment of the spleen as well as the prominent tail of the pancreas filled with gastric contents and intestinal loops as abnormal masses or fluid cisterns in the area of the splenic hilum. Furthermore, the pathologies of the hilum are discussed such as tumors of the splenic flexure of the colon, lesions arising from the left kidney or the left adrenal gland. The authors list characteristic imaging features of the most common focal lesions visualized in a standard ultrasound scan as well as enhancement patterns appearing in contrast-enhanced examinations. The article discusses the features and differentiation of, among others, infarction, splenic cysts including hydatid ones, abscesses and angiomas. The ultrasound appearance of lymphoma and secondary involvement of the spleen by other malignant neoplasms is also mentioned. Moreover, the authors provide useful tips connected with imaging techniques and interpretation of the findings. The ultrasound examination carried out in compliance with current standards allows for an optimal assessment of the organ and reduction of the error-making risk. This article is based on the publication of the experts from the Polish Ultrasound Society of 2005 and updated with the latest findings in pertinent literature. The photographic documentation, which provides images of the discussed lesions, is attached to this article.