Necrotizing enterocolitis (NEC) and fokal intestinal perforation (FIP) are two relatively common diseases that require neonatal surgical therapy. NEC affects 7% to 8% of extremely low bin weight infants and >30% of those with NEC require surgical intervensions. FIP appears to be a distinct clinical entity that occurs in 3% of very low birth weight infants. These two diseases are often confused and incorrectly treated. Although it is possible that isolated perforation is merely a focal form of NEC, clear differences in the natural history and pathologic findings in these two disorders contradict this hypothesis. Bowel with isolated perforation shows a local area with full-thickness necrosis and acute inflammation, whereas bowel with NEC shows edema, various degrees of inflammation, coagulation necrosis, bacterial invasion, and often areas of submucosal or subserosal gas. Indeed, both diseases likely result from similar factors that affect the perfusion, impairment of the facters that ensure immunologic defense and resistance to rupture of the bowel wall. In recent years, peritoneal drainage treatment is applied for intestinal perforation in extremely low birth weight babies. In this review we make the differential diagnosis of these two disorders and focus on peritoneal drainage to determine its indicatiens.