Irradiation of organic polymers by short pulses of far-UV (e.g., 193 nm) laser light causes ablative photodecomposition (APD) of the material. This etching process occurs cleanly leaving behind a well-defined pit. Longer wavelength (e.g., 532 nm) laser light also ablates material from a polymeric solid. However, this process is distinct from APD in that the sample near the pit is distorted and melted. Microscopic models are presented here for both the photochemical and thermal processes. The photochemical model predicts that well-defined pits will be formed, that narrow angular distributions of the ablated material should be observed, and that the average perpendicular ejection velocity will be 1000-2000 m/s. The thermal model predicts melting or distortion of the solid and a broad angular distribution of the ejected material.