The child, Krishna, was playing in the courtyard of his home at Farasu village in the district late last evening when a big cat pounced on him and took him into nearby forest, police said.
The child's kin chased the leopard but neither the big cat nor the child could be traced, they said.
Meanwhile, two suspected wildlife smugglers were held with leopard skin from the forest of Dhulkot in Dehradun last evening.
The arrested duo disclosed during interrogation that they had purchased the leopard skin in Chakrata area and were going to Dehradun to sell it.
The two -- Brijendra and Sanjay Kumar -- have been booked under the wildlife Protection Act and sent to jail, police said.