Charles Ellicott Commentary 2 Chronicles 8:6

"and Baalath, and all the store-cities that Solomon had, and all the cities for his chariots, and the cities for his horsemen, and all that Solomon desired to build for his pleasure in Jerusalem, and in Lebanon, and in all the land of his dominion." — 2 Chronicles 8:6 (ASV)

And Baalath. — 1 Kings 9:18. Like the two Beth-horons, it lay west of Jerusalem and was a bulwark against the Philistines: (compare to Joshua 19:44, a Danite town). The rest of this verse is identical with 1 Kings 9:19 (see that verse). (The Chronicler has twice added all.)

In the above section, no mention is made of the fortification of Jerusalem and the building of Hazor, Megiddo, and Gezer. This last city had been taken by Pharaoh and given by him to his daughter, Solomon’s wife (see 1 Kings 9:15–16). On the other hand, as we have seen, the Chronicler supplies several important details that are lacking in the parallel account.