We explore the on-resonance and off-resonance optical response of dielectric cylinders excited by normal incident plane waves. Both the analytical method, based on Mie theory, and the numerical method, implemented with the spectral element method, are undertaken in the study. We demonstrate that the whispering gallery mode characteristic of resonance behavior is strongly dependent on the refractive index and radius changes. Detuning of either parameter deteriorates the resonance action and creates yet another exciting phenomenon known as photonic nanojets. The subwavelength light focusing property can be associated with nanojets, and engineering the parameters yields strong field confinement and slowly diffracting beam propagation. The current work investigates the optical properties of the dielectric microcylinders at close proximity to the resonance condition. Both strong field focusing associated with photonic nanojets and enhanced field localization linked with the resonance condition are desired for photon manipulation scenarios in nanophotonics. © 2015 Optical Society of America.