I would suggest painting the inside too. It just gives it a more polished look. I did it when I painted my own cabinets. It`s a little more work but I`m glad I did it.

Many cabinets have a different surface in the interior - like a melamine. It is often a slightly different color, like the darker brown in your cabinet. When I painted my original cabinets - now in my laundry room - I painted both sides of the doors and the wood front frame of the cabinet including the sides of the frame piece, but not the inside of the cabinet itself. When you paint the side of the frame, mask off the edge of the darker area along the bottom, and if you do not remove the shelves, mask the edges of the shelfs near the frame so they don't get streaks of paint on them. If that is confusing, I can post a picture:)

I was not able to paint mines inside because they are melamine. I painted only outside, I have no choice. Looks good everybody loves it