Analysis of post-mortem liver for toxicological reasons is a considerable option when blood is unavailable. The development of analytical methods for tissue specimens is not as straightforward as for biological fluids as tissue presents challenges to the analytical chemist. The present study reports the development of a UHPLC-MS/MS method for the detection and quantification of 84 drugs and pharmaceuticals in human liver. The selected target drugs include pharmaceutical drugs and drugs of abuse. Sample preparation was studied using QuEChERS and different ratios of solvent volume and sample mass. Best results were attained by homogenizing 1 g of liver with acetonitrile KCO buffer (pH = 10), QuEChERS salts MgSO/ NaCl (1st purification step) and PSA/ 150 mg MgSO (2nd purification step). The extracted sample was analysed on UHPLC-MS/MS in multiple reaction monitoring mode (MRM) on a reversed-phase (Acquity BEH C18) column. Elution was accomplished by gradient program of mobile phase A: water, 0.1% formic acid and B: methanol, 0.1% formic acid that lasted 17 min. The method was specific, without interferences from the complex matrix. Sensitivity was satisfactory with limit of detection (LOD) ranging from 0.01 ng/g to 4.94 ng/g. Validation study was based on the guidelines of international bodies and included evaluation of recovery, carry-over, matrix effect, accuracy, stability, and precision of the method. The method performed satisfactory in relation to established bioanalytical criteria and was therefore applied to the analysis of liver tissue obtained post-mortem from chronic drug abusers, offering unambiguous identification and quantitative determination of drugs in postmortem blood.