The species Juniperus oxycedrus L. is a member of Cupressaceae family. The chemical composition and antiproliferative activity of wood and seeds essential oils of J. oxycedrus, grown wild in Lebanon, were evaluated in order to investigate whether these products could be used as sources of functional compounds. The most abundant components of the seeds essential oils were α-pinene, β-myrcene, limonene and δ-cadinene, while wood oil components included δ-cadinene, cis-thujopsene, Ï-muurolol, widdrol, epi-cubenol, β-caryophyllene and α-calacorene. Both wood and seeds essential oils inhibited the proliferation of K562 cell line with ic50 values of 39.8±2.7 and 147.7±3.6 μg/mL, respectively. The J. oxycedrus wood oil showed erythroid differentiation of 16.0±2.0% at a concentration of 5 μg/mL, while the seeds essential oil showed erythroid differentiation of 25.0±2.8% at a concentration of 50 μg/mL.