Abstract The effects of extractives, particle size, and crop species on the contents of structural carbohydrates, lignins, and micro-components in Canada Prairie Spring (CPS) wheat, durum wheat, barley, oat, and triticale straw, as well as flax shives, were determined. Extraction for 24 h in water followed by 7 h in ethyl alcohol (EtOH) yielded 20.2% extractives in triticale straw. Acid insoluble lignin decreased from 17.6% in native triticale straw to 13.6% in 24 h water + 7 h EtOH extracted triticale straw. The sample particle size influenced the values of glucan, xylan, acid insoluble lignin, ash, and extractives. Glucan, xylan, and acid insoluble lignin levels increased with increasing particle size. Protein, ash, and extractive levels decreased with increasing particle size. For flax shives, glucan, xylan, and acid insoluble lignin levels increased with increasing particle size from 19.1% to 33.2%, from 6.7% to 18.8%, and from 17.4% to 25.7%, respectively. The protein, ash, and extractive levels in flax shives decreased with increasing particle size from 6.5% to 1.9%, from 27.7% to 0.9%, and from 15.0% to 3.8%, respectively. Total glycans, lignin and extractive levels for the various straws, from the medium particle sized fraction, were 56.6–63.9, 14.7–19.4, and 6.8–20.2%, respectively. Total glycans, lignin, and extractives levels from the medium particle sized flax shives were 51.8, 25.8, and 6.46%, respectively. The composition of the medium particle size fraction reflected the composition of the corresponding original sample.