Methods and arrangements for resource allocation in a telecommunication system in which aggregation of component carriers is applied. The size of the resource allocation field is determined based on the transmission bandwidth of a selection of component carriers. The selection of component carriers comprises the component carrier on which the resource allocation message is monitored and the component carriers which are cross-scheduled from said component carrier. The resource allocation message comprising the resource allocation field with the determined size is transmitted to the user equipment over a particular component carrier of the selection of component carriers. Furthermore, with only one size of the resource allocation field a smaller number of code word sizes needs to be monitored by the UE. This leads to a smaller number of blind decodings performed in the UE. The present invention enables a more tailored approach when determining the size of the resource allocation field to avoid too high overhead but also a too coarse resource allocation.