The co-hydrothermal liquefaction of black pine wood (BPW) with Kukersite oil shale (KOS) at different blend ratios of BPW/KOS (1:1, 1:2, and 2:1) was conducted at 300 degrees C for 30 min. No synergistic effects on oil yields from the co-hydrothermal processing have been observed. However, when the methanol was substituted with hot compressed water as the solvent, positive synergistic effects on the oil yields were observed for all blend ratios, but the heating values of the oils from hydrothermal processing were higher than those from supercritical methanol processing under identical conditions. Co-hydrothermal liquefaction of BPW with KOS produced oils with less oxygen than those from co-supercritical methanol processing of BPW with KOS under identical conditions. The highest heating value from co-processing was 30.22 MJ/kg, which was obtained from the co-hydrothermal liquefaction of BPW with KOS at a blend ratio of 1:2. Oils from the co-hydrothermal liquefaction of BPW with KOS contained phenols, acids, ketones, and aldehydes. Guaiacol was the primary compound detected in the oils from co-hydrothermal processing. The relative yield of this compound was highest at a blend ratio of 1:2 (BPW/KOS). The prominent compounds in oils from the co-supercritical methanol processing were esters and phenols.