Optimization of microwave-assisted liquefaction of oil palm empty fruit bunch fiber (EFB) and cellulose (EFBC) in ethylene glycol (EG) was carried out to produce polyols. The liquefaction residues and hydroxyl numbers of the resultant polyols from respective sources were studied and compared. EFB produced a minimum residue of 3.22% at the optimal parameters of 160 degrees C and 15 min. Meanwhile, optimum liquefaction of EFBC produced 1.03% residue at 175 degrees C and 40 min. The maximum hydroxyl numbers of both EFB (749.22 mg KOH/g) and EFBC (639.91 mg KOH/g) polyols were obtained at optimum conditions. FTIR analysis revealed the degradation mechanism of cellulose and lignin in EFB at different temperatures. Lignin was found to be liquefied easily at lower temperatures (130 and 145 degrees C). However, most of the cellulose began to be liquefied at the optimum temperature (160 degrees C) and severely degraded at higher temperatures (175 and 190 degrees C).