Frequently asked questions How much cannabis can I possess in Rhode Island with an MMJ Card? In Rhode Island, you can possess the following amounts with a valid MMJ Card: – Possession Limit (Flower): Up to 2.5 oz. on-person. – Possession Limit (Flower): Up to 10 ounces on one’s own property, residential or non-residential. – Possession Limit (Concentrate): 1 gram concentrate = 3.3 grams flower. This suggests a possession limit of just over 1 oz. of concentrate.