In this study, we investigated the influence of frequency, film thickness, and SiO2 content on the dielectric constant (K) and loss tangent (tan delta) of liquid crystalline polyimide (LCPi) and liquid crystalline polyimide/SiO2 (LCPi/SiO2) nanocomposites in a high frequency environment. We tested the loss tangent of the LCPi and LCPi/SiO2 nanocomposites within the high frequency 1 MHz to 3 GHz range, and determined its value to be between 0.01 and 0.001. In addition, we found a formant for frequencies ranging from 0.5 GHz to 1 GHz. We also inferred from the dielectric loss graphs of films with different thicknesses that the formants of the loss tangent shifted toward higher frequencies with increasing thicknesses. When measuring the dielectric constant at high frequencies, we found that the dielectric constant decreased markedly with increased SiO2 contents. Using the dielectric constant of high-frequency circuit board materials as the standard, the dielectric constant of the LCPi/SiO2 nanocomposites at the frequency range from 1 MHz to 3 GHz was found to be as high as 2.2-3.4, thereby confirming the viability of LCPi/SiO2 nanocomposites as candidate materials for high-frequency circuit board. In addition, the volume resistivity (rho(V)) of the LCPi and LCPi/SiO2 nanocomposites also increased with increased SiO2 contents. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 117: 3454-3459, 2010