Necrotising enterocolitis is a serious disorder in preterm infants with a mortality of up to 60%. Therefore, early and precise diagnosis and rapid initiation of proper treatment are essential. Clinically suspected diagnosis is usually confirmed by typical findings on plain abdominal radiograph, for example, pneumatosis intestinalis, portal venous gas and, in case of intestinal perforation, pneumoperitoneum. Recently, there has been growing evidence that with real-time ultrasound, intramural air and portal gas can be better detected than with x-ray. Furthermore, ultrasound is able to assess the bowel wall directly and detect bowel wall thickening or thinning, reduced peristalsis or disturbed bowel wall perfusion. Intra-abdominal fluid, both intraluminal or extraluminal is also visible. However, data regarding the diagnostic validity and prognostic value of abdominal ultrasound are limited and often focused on a single finding rather than a combination of them. Additionally, until now, ultrasound findings seem to have little influence on therapeutic decisions. Therefore, the value of abdominal ultrasound in the diagnosis of necrotising enterocolitis has to be determined by further studies until its use can be generally recommended.