Novel phenyl-substituted (3a-3d, 4a, 5, 8a, 8b and 9a) and pyridyl-substituted (3e-3i, 4b, 8c-8e, 9b and 9c) isoindolines were prepared in the reaction of o-phthalaldehyde and corresponding substituted aromatic and heteroaromatic amines by modification of reaction conditions from low to high temperature and from neutral to acidic environment. The antiproliferative activity of chosen substituted isoindolines was assessed on a panel of tumour cell lines and normal human fibroblasts. The majority of tested compounds was active at the highest tested concentrations phenyl-substituted isoindolines 3a and 3b and pyridyl-substituted isoindoline 3g showed a selective effect at micromolar concentrations on HepG2 cell line in comparison with other tested tumour cell lines and normal human fibroblasts. The strongest yet non-selective effect was observed for the pyridyl-substituted isoindoline 8c. These isoindoline derivatives showed diverse mechanism of action on tumour cell death induction as compounds 3a and 8c probably induced mitotic catastrophe while compound 3b induced apoptosis. Indeed, DNA binding properties evidenced that compounds 8a, 8c and 8d bind to DNA as highly potent DNA intercalators. By contrast, compounds 3b, 3e, 3i, 4a and 5 did not target the DNA. At last, the phenyl-substituted compound 8b proved to be a strong DNA binding compound with sequence selective binding and without DNA intercalation profile.