The objective of this study was to evaluate the role of cytochrome P450 monooxygenases (P450s) and other detoxification-related proteins in Imisun sunflower resistance. Two sunflower inbred lines were used: HA 425 and HA 89, imidazolinone (IMI)-resistant and susceptible, respectively. Growth response to imazethapyr herbicide in combination with P450s inhibitors 1-aminobenzotriazole (ABT) and piperonyl butoxide (PBO) was evaluated in 15-day-old sunflower plantlets. Roots were collected and label-free quantitation (LFQ) proteomic analysis were carried out in order to characterize plant response to IMI. Roots of 15-day-old plants treated with 0 and 3.3 µM imazethapyr were frozen in liquid nitrogen. Protein extraction was performed as described in Wu et al. (2014) from 1 g root tissue per genotype/treatment combination.