Cultivated sunflower (Helianthus annuus L.) is grown worldwide as an oilseed crop, however, evidence suggests that sunflower can also be used as a dual use crop and harvested as a source of lignocellulosic biomass. To gain a better understanding of the genetics of wood chemistry and biomass related traits in sunflower a H. annuus x (H. annuus x H. argophyllus) BC1 population (n=525) and a H. annuus (elite x landrace) recombinant inbred line population (RIL) (n=169) were evaluated in multiple locations [(BC1 – Athens, GA; Ames, IA; Vancouver, BC), (RIL – Athens, GA)] in 2009. Stem sections were analyzed using a pyrolysis Molecular Beam Mass Spectrometer (pyMBMS) and biomass related traits (e.g. days to flower, plant height, total and/or main stem biomass, stem diameter and basic specific gravity) were phenotyped. The BC1 population was genotyped with a 384 BeadXpress SNP array and the RIL population was genotyped with a 10,640 SNP Infinium Chip (both from Illumina). Genetic maps each with 17 LGs were created; the H. annuus x H. argophyllus BC1 map was 1942 cM/285 loci and the H. annuus (elite x landrace) RIL map was 1407 cM/3117 loci. Novel QTL for plant biomass and stem density were identified using CIM. QTL for S- and G-lignin were clustered on LGs 5, 16, 17 and QTL for carbohydrate content (celluloses, hemicelluloses) were clustered on LG7. QTL for ratios of cellulose/lignin, S/G lignin and hemicellulose/cellulose were clustered at the bottom of LG17. Most QTL were small (PVE <15%) or medium effect (PVE = 15-25%).