Yes, ADP is found in mitochondria.
Mitochondria are considered the powerhouses of a cell. Chemical energy produced by these cellular structures are stored in ATP (adenosine triphosphate). When needed by the cells to perform some cellular function, ATP is transported from the mitochondrial matrix to the cytoplasm where they are then easily assessable to the cell. To release the necessary energy, ATP breaks off its 3rd phosphate group and gets converted to ADP (adenosine diphosphate), which has only 2 phosphate groups. This free ADP is transported from the cytoplasm back to the mitochondrial matrix where it undergoes oxidative phosphorylation to produce ATP. This is a continuous cycle so ADP is continuously being transported in and out of the mitochondria.