There seems to be some confusion or mixing of campgrounds in the Dyrt reviews.  There are only two campgrounds at Lava Lake and one at Little Lava Lake which is right next door.  

I did not see any dispersed campsites. However, there is a private campground run by the Lava Lake Resort and you can only make reservations there by phone (541-382-9443).  Their campground is the only one with full hookups, power, water and sewer.  This is also the only dump site in the area and costs $10.  They also have propane, gasoline, showers and a small camp store.

The NFS Lava Lake Campground has nicely spaced sites, but not large parking areas.  They only have 2 or 3 drinking water sources and because they are not threaded you will need a bucket or 'Water Bandit' to fill you fresh water tank.  I saw only 1 or 2 places tent campers could dump their dishwater.  There are no showers, but the vault toilets were exceptionally clean, odorless and well stocked with TP.  We were able to get 1-3 bars on our Verizon phones that took a while to eventually send photos.

We were there mid June, 2021, and the mosquitoes were moderate, but well controlled with repellant.  The lake had a toxic algae bloom and was closed to swimming and pets.  What we really enjoyed were the many trails that were nearby along the Cascade Highway, like Blue Lagoon and Lucky Lake, non of which required advance reservations.