Three linear low density polyethylene (LLDPE) resins of similar melt index and density were synthesized with different comonomers in the Unipol pilot-plant scale reactor. The molecular structure, blown film morphology, and film strength properties of the resins have been comprehensively characterized. The film dart drop impact strength of the LLDPEs increases in the order of ethylene/1-butene, ethylene/1-octene, and ethylene/1-hexene copolymers; whereas the Elmendorf tear strength of them increases in the order of ethylene/1-butene, ethylene/1-hexene, and ethylene/1-octene copolymers. The mechanical properties seem to be highly associated with the length and distribution of short chain branches and, consequently, the lamellar thickness distribution of the resins.