Hexagonal micropillar (μ-pillar) cavities have been studied using 2-D finite-difference time-domain (FDTD) method. Singlemode resonances have been observed from a 2-μm sized hexagonal μ-pillar cavity that is selectively input-coupled. The simulated resonance wavelengths are consistent with the wavefront-matching condition based on ray-optics. The resonant field distribution has an integer number of field maxima along the cavity rim similar to whispering-gallery modes. Laterally waveguide-coupled hexagonal μ-pillar cavity channel add/drop filters with parallel and non-parallel waveguides have also been designed and simulated. Preliminary simulation of a 20-μm sized hexagonal μ-pillar cavity laterally coupled with 0.4-μm wide parallel waveguides demonstrated an extinction ratio of ≈ 8 dB, a signal/background ratio of ≈ 11 dB and a finesse of ≈ 5.