A new family of compounds (4-acyl isochroman-1,3-diones), demonstrating antioxidant properties, have been synthesized and described. Their antioxidant properties are studied herein. These antioxidant characters increased with the electronic withdrawing character of the acyl substituent. So, 4-p-Cyanobenzoyl isochroman-1,3-dione and 4-p-Nitrobenzoyl isochroman-1,3-dione have been found to exhibit a reducing power and to scavenge the DPPH • free radical using FRAP and DPPH assays..