The neural infrastructure for sentence production and comprehension has been found to be mostly shared. The same regions are engaged during speaking and listening, with some differences in their loading depending on modality (Giglio et al., 2022). In this fMRI study (n=40), we investigated whether modality affects the connectivity between inferior frontal and temporal regions, previously found to be involved in syntactic processing across modalities, and with the cerebellum, which has been historically linked with motor aspects of production. Participants produced or listened to word sequences of increasing constituent size. We found that constituent size reliably increased the connectivity between the inferior frontal gyrus and the posterior temporal lobe in both modalities. Preliminary cerebellar results suggest that different sub-regions presented different patterns of connectivity. Connectivity between Lobule VI and (pre)motor regions was increased during production relative to comprehension. Connectivity between Crus I/II and fronto-temporal regions was instead increased as a function of constituent size, and in particular during production. These results thus show that the connectivity between fronto-temporal regions is upregulated for syntactic structure building in both sentence production and comprehension, while cortico-cerebellar connectivity is enhanced both in response to syntactic processing and during production.