To provide a positional information providing system, an electronic tag, and a personal digital assistance capable of detecting an installation position of a prescribed object with high positional accuracy, even indoors or underground without requiring complex processes.

An electronic tag 30 is attached to an object installed statically, and the positional information indicating the installation position of the object is stored in an electronic tag. The electronic tag responds to electric waves and transmits electronic tag information, including the positional information, when it receives a prescribed electric wave from the personal digital assistance 10. The personal digital assistance receives the electronic tag information and notifies the installation position of the electronic tag to a user of the personal digital assistance, by informing the positional information included in the tag by a video, an image, or voice or the like.