Provided are a method and an apparatus for performing, by a first device, wireless communication. The method may comprise the steps of: receiving, from a base station, first information related to SL synchronization priority; receiving, from the base station, second information indicating whether a base station-related synchronization reference can be selected as a synchronization source; and performing synchronization according to one synchronization reference of a GNSS-related synchronization reference and other terminals on the basis of the second information indicating that the base station-related synchronization reference cannot be selected as a synchronization source.