Why doesn't htop display the same processes as top?

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http://askubuntu.com – I have a home server sometimes running at a high CPU usage rate of about 50 to 70 percents. In htop, my favorite process manager, I can sort the processes by CPU usage, but often there isn't any process consuming more than 0 % CPU. On the other side, htop displays the whole CPU usage of the system which is about 50 percents, as said before. I guess that there is an easy explanation for this, but I don't know it. Maybe there are some hidden processes? But even running it as root doesn't show more processes. EDIT: I looked into top, which is showing (at least) two more processes: 230 roo (HowTos)