Two new organic superconductors and a semiconductor were the subject of angular- and temperature-dependent ESR (electron spin resonance) studies. The low-T-c (4.0 K) K-L-(ET)(2)Cu(CF3)(4)(TCE) phase gave room-temperature line widths and g values between 68 (Delta H-parallel to) and 54 (Delta H-perpendicular to) G and between 2.0052 (g(parallel to)) and 2.0097 (g(perpendicular to)), respectively. Its low-temperature behavior can be qualitatively correlated to four-probe resistivity measurements and described with the use of Elliott’s formula. The high-T-c (9.2 K) K-H-(ET)(2)Cu(CF3)(4)(TCE) phase gave a narrow line width range of 6.2 (Delta H-parallel to) to 5.8 (Delta H-perpendicular to) G and corresponding g values of 2.0081 (g(parallel to)) to 2.0105 (g(perpendicular to)), respectively. The solvent-free semiconductor (ET)(2)Cu(CF3)(4) revealed a characteristic line width between 30 and 40 G, thus providing a facile characterization of the three ET/Cu(CF3)(4)(-) phases based on their ESR peak-to-peak line widths. X-ray studies on the semiconductor indicated a similar unit cell compared to the previously reported alpha-(ET)(2)Ag(CF3)(4) phase. Superconducting K-L- and K-H-(ET)(2)CU(CF3)(4)(TCE) crystals lost their cocrystallized solvent, TCE, at 340 and 380 K, respectively, and were converted to semiconducting (ET)(2)Cu(CF3)(4), indicating the close relationship among these three compounds.