i-scan technology is the newly developed image-enhanced endoscopy technology from PENTAX, Japan. This consists of three types of algorithms: surface enhancement (SE), contrast enhancement (CE), and tone enhancement (TE). SE enhances light-dark contrast by obtaining luminance intensity data for each pixel and applying an algorithm that allows detailed observation of a mucosal surface structure. CE digitally adds blue color in relatively dark areas, by obtaining luminance intensity data for each pixel and applying an algorithm that allows detailed observation of subtle irregularities around the surface. Both enhancement functions work in real time without impairing the original color of the organ, therefore, SE and CE are suitable for screening endoscopy to detect gastrointestinal tumors at an early stage. TE dissects and analyzes the individual RGB components of a normal image. The algorithm then alters the color frequencies of each component and recombines the components to a single, new color image. This is designed to enhance minute mucosal structures and subtle changes in color. TE works in real time and consists of three modes such as TE-g for gastric tumors, TE-c for colonic tumors, and TE-e for esophageal tumors. TE is suitable mainly for detailed examination of the lesions that are detected in a screening endoscopy. i-scan technology leads us to easier detection, diagnosis and treatment of gastrointestinal diseases.