Quirino, officially the Province of Quirino, is a landlocked province in the Philippines located in the Cagayan Valley region in Luzon. Quirino is the 8th smallest province in the country in terms of both population and area. the Its capital is Cabarroguis while Diffun is the most populous in the province. It is named after Elpidio Quirino, the sixth President of the …Quirino, officially the Province of Quirino, is a landlocked province in the Philippines located in the Cagayan Valley region in Luzon. Quirino is the 8th smallest province in the country in terms of both population and area. the Its capital is Cabarroguis while Diffun is the most populous in the province. It is named after Elpidio Quirino, the sixth President of the Philippines.