Water that maintains its liquid state in the temperature range from 100°C to 374°C is called subcritical water, compressed hot water or pressurized hot water. This type of water has unique properties compared to ambient water. One is a low relative dielectric constant and another is a high ion product. Due to these properties, this water can be used to extract functional substances from natural resources. In this article, the application of subcritical water for the extraction of substances from agricultural products or their wastes is reviewed.