It became the capital of Portuguese Guinea in 1942 , and has been the capital since independence was declared , except for a short time in 1973 and 1974 when the capital was at Boe . In 1942 it became the capital of Portuguese Guinea . After the declaration of independence by the anti-colonial guerrillas of PAIGC , in 1973 , the capital of the de facto independent territories was declared to be Madina do Boe , but Bissau remained as the capital of the Portuguese-occupied regions , and the de jure capital of the entire Portuguese Guinea .