A route selection assistance system enabling easy selection of a route of a living body lumen for delivering a medical instrument to a site within a living body via the living body lumen, a recording medium on which a route selection assistance program is recorded, and a route selection assistance method are disclosed. The route selection assistance system includes: a receiving section configured to receive an input of site information specifying a target site; an image obtaining section configured to obtain image information on a living body of a target patient; a route extracting section configured to extract a plurality of routes of a living body lumen; a ranking assigning section configured to assign rankings to the plurality of routes according to ease of delivery of the medical instrument and patient scores determined according to magnitude of a burden imposed on the target patient.