They had to give the island of Hong Kong to the British indefinitely, and the British would keep control of it all the way until the end of the 20th century. The Chinese had to pay for opium that they destroyed. They had to give reparations to the British to pay for the costs of the war. Now to add insult to injury, the British were not satisfied. And in 1856, you have the Second Opium War, where they try to extract even more concessions from China. After which, opium is legalized. The whole time, opium flooding into the country, and really undermining the social fabric of society.