In this paper, a coding scheme with M-ary Walsh-Hadamard (WH) orthogonal modulation is considered for multi-carrier (MC) transmission. A novel pilot-assisted channel estimation approach is proposed, that efficiently exploits the properties of WH codes. Firstly, simulation results on the single-user performance show the influence of the energy distribution between pilot and information symbols. Then, the impact of the channel estimation method is assessed for different system loads in a MC code division multiple access (MC-CDMA) uplink scenario.