In this paper, several performance analysis metrics for the cyclic prefix-based single-carrier (CP-SC) opportunistic cooperative diversity systems are presented. After the statistical evaluation of the end-to-end signal-to-noise-ratio of a two-hop relaying transmission, we derive tight upper bounds for the maximum achievable average rate and lower bounds for the outage probability in closed form. Further, asymptotic analysis on the outage probability reveals that the diversity gain is determined by both the number of relay nodes in the system and the number of channel taps being supported by the CP length. Simulation results verify the derived closed-form analytical expressions and also the diversity gains. Asymptotic performance is also verified via Monte Carlo simulations.