Cognitive radio (CR) networks are attracting massive attention as means to alleviate spectrum scarcity. In order for the CR users to opportunistically utilize the spectrum in absence of primary users (PUs), a reliable cooperative spectrum sensing scheme should be employed to assure service quality for the PUs as well as spectrum accessibility for the CRs. In this paper, a hybrid soft-hard decision fusion scheme of cooperative sensing is proposed. The hybridization of soft-hard fusion is realized by means of two-stage hierarchical clustering to jointly exploit the advantages of soft and hard fusion schemes. Through computer simulations, the proposed cooperation scheme is proven to have promising overall balanced-performance. However, it has been also shown that the overall performance of the CR network would be very much dependent on some existing tradeoffs between detection reliability and radio resources.