A method of generating a data block for performing a polling procedure in a wireless communication system, a method of transmitting data and a method of performing a polling procedure are disclosed. A protocol layer performs the polling procedure for requesting a receiving side to transmit status report if there are no data to be transmitted to the receiving side in both a transmission buffer and a retransmission buffer. When determining whether there are no data to be transmitted to the receiving side in the retransmission buffer, it is preferable that a data block for which retransmission request information is not received from the receiving side is excluded.