Catalytic co-conversion of Kraft lignin (KL) and linear low-density polyethylene (LLDPE) over mesostructured catalysts was examined using a micro-pyrolyzer equipped with gas chromatography-mass spectrometry/flame ionization detector (MPy-GC/MS/FID). Mesoporous catalysts of Al-SBA-15 and mesoZSM-5 were synthesized and characterized by N-2 sorption, ammonia temperature programmed desorption, and X-ray diffraction. The characterization results indicated that mesoZSM-5 had the smaller average pore size (4.10 nm) than Al-SBA-15 (10.70 nm), but its total acidity (both weak and strong acid sites) was much higher than Al-SBA-15. When they were applied as catalysts in the pyrolysis of KL and LLDPE, the mesoZSM-5 exhibited higher catalytic activity for aromatic hydrocarbon production due to its higher acidity and MFI pore structure. Indeed, synergistic synthesis of aromatic hydrocarbons was achieved via the catalytic co-pyrolysis of KL and LLDPE because of the H-donating effect of LLDPE; the experimental yields (GC/MS area; abundance vs. time) of aromatic hydrocarbons in the oils obtained from catalytic co-pyrolysis of KL/LLDPE (1:1) over Al-SBA-15 (8.76x10(7)) and mesoZSM-5 (27.58x10(7)) were similar to 1.5 fold higher than the theoretical yields.