The goal of this study was to examine the effect of the linguistic distance between a first language (L1) and a second language (L2) on neural activity during second language relative to first language processing. We compared different L1–L2 pairs in which different linguistic features characterize linguistic distance. Chinese and Korean native speakers were instructed to perform sentence comprehension tasks in two L2s (English and Japanese) and their respective L1s. Activation while understanding English sentences relative to understanding sentences in L1 was greater for the Korean group than the Chinese group in the left inferior frontal gyrus, bilateral posterior superior temporal gyri, and right cerebellum. Activation while understanding Japanese sentences relative to understanding sentences in L1 was greater for the Chinese group than the Korean group in the anterior portion of the left superior temporal gyrus. The results demonstrated that the location of the L2–L1 processing-induced cortical activation varies between different L1–L2 pairs.