A communication device for handling a radio resource control, RRC, connection, comprising: a storage unit for storing instructions; and a processing circuit, coupled to the storage unit, configured to execute the stored instructions in the storage unit of: transmitting a first resume request message with a first resume identity for requesting a resume of the RRC connection to a first cell of a network; characterising by receiving a resume reject message from the first cell of the network in response to the transmitted first resume request message; and if the received resume reject message comprises an indicator, then the communication device determines that both the first resume identity and at least one radio resource corresponding to the first resume identity are valid, and the communication device is configured to keep both the first resume identity and at least one radio resource; and if the received resume reject message does not comprise the indicator, then the communication device determines that both the first resume identity and the least one radio resource corresponding to the first resume identity are invalid, and the communication device is configured to release both the first resume identity and the at least one radio resource. a storage unit for storing instructions; and a processing circuit, coupled to the storage unit, configured to execute the stored instructions in the storage unit of: transmitting a first resume request message with a first resume identity for requesting a resume of the RRC connection to a first cell of a network; characterising by receiving a resume reject message from the first cell of the network in response to the transmitted first resume request message; and if the received resume reject message comprises an indicator, then the communication device determines that both the first resume identity and at least one radio resource corresponding to the first resume identity are valid, and the communication device is configured to keep both the first resume identity and at least one radio resource; and if the received resume reject message does not comprise the indicator, then the communication device determines that both the first resume identity and the least one radio resource corresponding to the first resume identity are invalid, and the communication device is configured to release both the first resume identity and the at least one radio resource. transmitting a first resume request message with a first resume identity for requesting a resume of the RRC connection to a first cell of a network; characterising by receiving a resume reject message from the first cell of the network in response to the transmitted first resume request message; and if the received resume reject message comprises an indicator, then the communication device determines that both the first resume identity and at least one radio resource corresponding to the first resume identity are valid, and the communication device is configured to keep both the first resume identity and at least one radio resource; and if the received resume reject message does not comprise the indicator, then the communication device determines that both the first resume identity and the least one radio resource corresponding to the first resume identity are invalid, and the communication device is configured to release both the first resume identity and the at least one radio resource.