slow running water

Valves get dirt and stuff stuck in them. If the problem is on both the hot and cold, then check further down the line. If the other hot and colds are all good, then maybe you've got frozen pipes.

The problem is only on the cold side.

when was the house built? do you have galvanized supply lines? if you have galvanized lines they could be rusted and this restricts water flow. please respond.

Fish

No I have copper piping from a house that was re-plumbed about 10 years ago.

I agree with most of the answers that it does sound like a valve, likely the one you are thinking of, but don't eliminate the possibility it is the shut off valve that is under the sink.

As mentioned you probably need to replace the angle stop( compression valve) If the existing angel stop is a compression fitting from the supply stub out 1/2" copper you need a 5/8 Compression to 3/8 compression. There might not be enough pipe sticking out from the wall to cut the compression ring off and add a new one.( they do make a puller, Vie cut them off be careful) What you might do is take the old one with you find one that the compression nut fits the old one. Before you put it back together if you can try to blow some water out of the line, there might some debris in there. You might have a angle stops with the supply line attached ( cheap junk) so you might need the right supply lines. When you put back together use pipe dope on compression ring and compression nut threads. When you have it all back and it all looks good leave a piece of newspaper under the sink for a day any small wet spots will indicate a leak.

Thanks everyone. I replaced the compression fitting in less that 10 minutes and my water pressure is normal.

Right-on.

if you didnt replace the hoses that feed the faucet, one hot one cold it might be the cause.

those flexible lines can cause this, the inside rubber tube detoriates

had a bad case of that with my hand held shower