Your comportment is the way you act, especially when you behave well. You might compliment a patient little boy on his comportment as he waits in line for a turn on the swings.
You can use the noun comportment to describe both the way a person behaves and also the way he carries himself — his general manner. A queen's comportment is usually regal, a bit stiff, and dignified. The comportment of a bunch of little kids at an amusement park is very different. The Middle French root is comportement, "bearing or behavior," from the Latin comportare, "to bring together or collect."