BACKGROUND: Hemiparetic patients lose the ability to move their trunk selectively, abdominals are affected and neither voluntary nor reflex activity is present. OBJECTIVE: To investigate if the inclusion of specific exercises for the trunk muscles in a rehabilitation program for chronic hemiparetic patients could lead to an additional improvement. METHODS: A multiple-participant single-subject design was replicated in patients with hemiplegia. The study was conducted in two cycles: for the first cycle (A), patients received conventional rehabilitation program, then for the second cycle (B), six months later, the same subjects received conventional rehabilitation therapy plus an additional specific selective trunk muscles training. Trunk Impairment Scale (TIS), Berg Balance Scale (BBS), 10 meters distance walk test (10 MWT), Functional Independence Measure (FIM) and instrumental gait analysis were performed before and after both treatment cycles. RESULTS: Significant changes were observed in TIS and 10 MWT after the two treatment cycles. However, after treatment cycle B, BBS and FIM score showed an additional improvement. Whereas, after treatment cycle A gait analysis did not relevantly changed, but after cycle B a significant improvement was registered in velocity, cadence and percentage of stance in the gait cycle. CONCLUSIONS: In our patients, the training for selective activation of the trunk muscles had led to a consistent improvement of gait analysis parameters, and hemiparesis-related disability in stance and activities of daily living.