LiCoPO4 (TN ≈ 21.8 K) & LiMnPO4 (TN ≈ 34 K) are antiferromagnetic insulators exhibiting large magnetoelectric effects. We performed inelastic neutron scattering (INS) experiments to investigate the spin dynamics of these systems and analyzed the measured magnetic spectra by linear spin-wave theory, taking into account intra- and inter-plane nearest, next nearest neighbor magnetic exchange interactions and single ion anisotropy. The INS results indicate that the single ion anisotropy in LiCoPO4 is comparable to the nearest-neighbor magnetic exchange interaction rendering Ising-type behavior of LiCoPO4. Neutron diffraction studies of LiMnPO4 in applied magnetic fields reveal a spin-flop transition at ~ 3.5 Tesla with characteristics of a second order phase transition.