In this paper a comparative study of two measurement campaigns carried out in Barcelona, Spain, and Pozna, Poland, to identify spectrum occupancy in different bands, is presented. In both cases the measurement setup was harmonized to obtain comparable results. The problem of efficient noise floor estimation was also considered and a pragmatic approach that takes into account both internal and ambient noise has been proposed. Obtained results show significant amount of unused spectrum, with similar results for both sites when analyzed globally (average spectrum occupancy of 27% in Pozna¿ and 22% in Barcelona). On the contrary, when going to the detailed analysis of some specific bands, more relevant differences are obtained. These differences have been observed mainly in the Terrestrial TRunked RAdio (TETRA) bands that in Poland are also used by Code Division Multiple Access (CDMA) 450, as well as in the bands of theGlobal System for Mobile communications (GSM) due to the effects of Universal Mobile Telecommunications System (UMTS) refarming in the 900 MHz band. ; Peer Reviewed ; Postprint (published version)