The accumulation of phenylpropanoids compounds has significant role in resistance mechanisms at post-attachment and post-haustorial interaction. Lignin is a phenolic polymer mainly deposited in secondary cell wall during the last stages of cell differentiation and provides enhanced mechanical strength and a water-impermeable barrier. There are some investigations reporting the lignification, vessel occlusion, cell wall deposition (Labrousse et al. 2001) and overexpression of two genes (phenylalanine ammonia-lyase - PAL and cinnamate-4-hydroxylase - C4H) in Helianthus infected by Orobanche cumana (Letousey et al. 2007). This study includes the data related to the transcriptional activity of four genes - PAL, C4H, 4CL1 and FAH1, involved in lignin metabolism, correlated with the analysis of phenylalanine ammonia-lyase activity and histochemical investigations of root tissue in sunflower resistant (Favorit and PR64LE20) and susceptible (Performer) genotypes to O. cumana. Experiences have been realized in pots with sterilized soil – uninfected (control) and infected with broomrape seeds. The biologic material (roots) was collected in temporal dynamics during the four development phases of pathosystem, within 67 days. The crosssections were stained with Safranin O. The PAL activity was measured spectrophotometrically at 290 nm by using trans-cinnamic acid substrate. Transcript accumulation of genes was assayed by real-time PCR using specific primers. There are no differences in lignin deposition but have been ascertained variations of enzyme activity and expression of genes between resistant and susceptible genotypes in normal (uninfected) conditions of cultivation. The comparative analysis of two experimental models in the background of infection: pathogen-host incompatibility (Favorit and PR64LE20) and pathosystem (Performer) has been demonstrated different expression profiles for the same physiological reaction (resistance). In the incompatible combination of the hybrid Favorit - O. cumana the manifestation of response reactions to stress in the background of infection beginning 35 days after cultivation through increasing of lignin content and PAL activity with indirectly correlate with the relative expression genes. The PR64LE20 genotype has displayed a defense response almost throughout the all analyzed period, expressed predominantly by the repression of the mRNA synthesis of the four genes and the PAL. Significant intensification of the stress state was manifested by the more intensive accumulation of transcripts. The lignin content and PAL activity have been established in the case of pathosystem Performer - O. cumana at the stage of underground stems and flowering shoots.