Sinusitis and other disorders of the ear, nose and throat are diagnosed and/or treated using minimally invasive approaches with flexible or rigid instruments. Various methods and devices are used for remodeling or changing the shape, size or configuration of a sinus ostium or duct or other anatomical structure in the ear, nose or throat; implanting a device, cells or tissues; removing matter from the ear, nose or throat; delivering diagnostic or therapeutic substances or performing other diagnostic or therapeutic procedures. Introducing devices (e.g., guide catheters, tubes, guidewires, elongate probes, other elongate members) may be used to facilitate insertion of working devices (e.g. catheters e.g. balloon catheters, guidewires, tissue cutting or remodeling devices, devices for implanting elements like stents, electrosurgical devices, energy emitting devices, devices for delivering diagnostic or therapeutic agents, substance delivery implants, scopes etc.) into the paranasal sinuses or other structures in the ear, nose or throat.