Small-angle X-ray scattering (SAXS) studies of electrically conductive blends based on polyaniline-dodecylbenzenesulfonic acid (PANI-DBSA)/styrene-butadiene-styrene (SBS) triblock copolymer were performed to investigate the influence of the blend preparation procedure on the nanoscopic structure of the blends. The blends were prepared by mechanical mixing (MM) procedure and by in situ polymerization (ISP) of aniline in the presence of SBS. The results indicate that pure PANI-DBSA presents an extended phase consisting of crystalline islands of nanometric size, with a good spatial correlation between them, embedded into an amorphous PANI phase. This feature was not observed in SBS/PANI-DBSA blends prepared by MM or ISP. In MM blends, the PANI phase is constituted by smaller domains, containing poorly spatially correlated crystalline islands, whereas in ISP blends with low or medium amount of PANI, there is no SAXS peak which could be related to a spatial correlation between PANI crystalline islands. The conductivity of the ISP blends is higher when compared to MM blends because of the higher homogeneity at nanometric scale. (c) 2007 Wiley Periodicals, Inc.