Objective: To evaluate differences in yield and composition of the essential oil and antioxidant contents in 71 diffusa plants from localities in central region of Tamaulipas. Methods: Samples were collected in Tamaulipas, Mexico in the arid zone. Essential oil was obtained through steam distillation and analyzed using GC-MS. Polyphenol contents, antioxidant activities using ABTS and ferric reducing antioxidant power (FRAP) methods also were evaluated. Results: A total of 21 compunds were identified in the essential oils: nevertheless, only Eucalyptol. I.4-Methanocyctooctajdjpyridazine.,4,4a.5.6.9,10,10a-octahydro-I 1,1 1-dimethyl-, (1a,4a.4aa.10aa) y Ethanone, 1-(1,3-dimethy1-3-cyclohexen-l-yl) were detected in the three sites. Fliehest contents were registered in the sample from Padron y Juarez with phenolic content of 33.85 mg GAE/g of dry material and antioxidant activities with ABTS 72.32% and with FRAP 21.33 mg GAE/g of dry material. Statistical differences were observed in essential oil. phenolics and antioxidants contents between populations. Conclusions: Results suggest that climatic differences and origin influence the phytochemicals in the medicinal plant T. difusa. and thus. it is worth to consider such effects for industrial and medicinal purposes.