There is provided a method, performed by a network node (e.g. an RNC), for detecting a neighbor cell relation between different radio access technologies in a cellular communication network. The method comprises the step (S1) of triggering a User Equipment, UE, served in a first cell of a first radio access technology (e.g. WCDMA cell) under the control of the network node (e.g. RNC), to perform a cell selection process by initiating a connection release with redirection to a second radio access technology (e.g. GSM), causing the UE to select a second cell of the second radio access technology (e.g. GSM cell). The method also comprises the step (S2) of receiving information representing the identity of the second cell selected by the UE (e.g. CGI), and the step (S3) of identifying, based on the received information representing the identity of the second cell and information representing the identity of the first cell, a neighbor cell relation between the first cell and the second cell. In this way, an efficient way of detecting a neighbor cell relation between different radio access technologies is provided.