West Ham boss David Moyes said: "I'm disappointed because we didn't win. We did OK but we gave away a couple of really poor goals.
"The penalty was the turning point, we started OK and contained them a little bit but we lacked that bit of quality and we didn't keep the ball when we won it. We hadn't done badly up till then.
"The same situation happened in the second half as well. We got ourselves back in the game and looked threatening but the second goal was a killer and we were punished.
"Brighton are a good team. I did think we had done better in some parts today against them that we had in the past but it doesn't show in the result."