In this study we contrast the behavior of an amorphous polyetherimide (ODPA-P3) with that of a semi-crystalline one (BPDA-P3) on introducing single-wall carbon nanotubes (SWCNTs; 0.1-4.4 vol.%). The SWCNTs act as a nucleating agent and induce crystallinity (up to 45%) in amorphous ODPA-P3; in BPDA-P3, the SWCNTs lower the onset of crystallization during thermal imidization, but decrease the overall degree of crystallinity. Tensile tests show that the yield strength is the same for both polyimides up to 0.3% SWCNT loadings. Above this concentration the yield strength for the BPDA-P3 nanocomposites remains constant whereas in the ODPA-P3 nanocomposites it increases from 80 to 126 MPa (1.2 vol.%). In the amorphous PEI, SWCNTs enhance the thermo-mechanical properties (Tg, storage- and elastic modulus, and yield strength), but in the semi-crystalline PEI there are little or no effects on the mechanical performance. (C) 2014 Elsevier Ltd. All rights reserved.