Despite significant improvements in preoperative tumor staging due to sophisticated new imaging and interventional techniques, peritoneal tumor spread and occult liver and lymph node metastases are only detected during surgery in some patients. Newer treatment modalities using neoadjuvant regimens are only given if occult tumor spread is excluded. Diagnostic laparoscopy has therefore been introduced to prevent patients with advanced tumor disease from unnecessary laparotomy and as a diagnostic tool in neoadjuvant treatment protocols. Laparoscopic ultrasound represents an important technical improvement in diagnostic laparoscopy. The main indication for diagnostic laparoscopy is therefore exact tumor staging, especially in terms of peritoneal, liver, and lymphatic tumor spread, whereas determination of local tumor resectability is not the main issue. The aim of the current review is to summarize the technique of staging laparoscopy and to discuss its clinical value for a variety of gastrointestinal malignancies.