In this paper, a quantum version of Diffie-Hellman key agreement protocol is developed using the commutative rotation transformations. Qubits rotated by secret rotation angles and exchanged over a quantum channel are appropriately measured to form a secret shared key. Additional 'slack' rotations are used to ensure that measurement of the commutative transformations always result in the same bit value, for legitimate party, in the absence of an eavesdropper. The performance of the quantum protocol is evaluated in terms of the number of exchanges needed for a given key size and the probability of detecting an eavesdropper. We also compare the proposed protocol with BB84.