A method is presented for implementing a cell change for a mobile station (MS) in a packet-switched cellular radio system comprising a first base station (BTSold), a second base station (BTSnew) and a controlling unit (PCU, PCUold) controlling the operation of at least the first base station (BTSold). The method comprises the steps of establishing at the controlling unit (PCU, PCUold) the knowledge about the mobile station's (MS) need for performing a cell change from the cell of the first base station (BTSold) to the cell of the second base station BTSnew) while the mobile station (MS) is still communicating with the first base station (BTSold), transmitting from the controlling unit (PCU, PCUold) towards the mobile station through the first base station (BTSold) a first message (207, 309, 410) in order to fix an oncoming first moment of lime (209) as the moment of performing cell change and from said first moment of time onwards (209) providing access for the mobile station to the cell of the second base station.