Warning: Read if you want details to help make decision about whether child should watch, don't read if you don't want spoilers. Ok, I'm three seasons into this show and have watched it evolve from Season 1 where Arrow is a full-on vigilante and kills most all who have "failed this City!" to where he comes back in Season 2 and decides he's not a murderer and wants justice more than sheer blood lust. That's a good thing. The not-so-good thing is that the show ups the violence in Seasons 2 and 3 by introducing villains who have no problem slaughtering people (now sometimes innocents who are collateral damage as they got in the way of the not-so-innocent targets) and hanging them upside down in warehouses to let the blood drain out of them. All shown, not implied. As the show progresses, so does the violence, a mother is gouged with a sword straight through center mass *in front of her children* and dies, eyes boggled wide open, as she falls to the ground next to them (they're all tied up). Another female character who is a vigilante gets brutally slain unexpectedly and falls off of a building onto a dumpster which breaks her back when she lands on the ground *directly at the feet of her sister*. Again, all shown in graphic detail, repeatedly if you count the "previously on Arrow" segments at the beginning of each show. So, that's the violence part. Then there is the romantic issue...it's not that they show sex so much as the way relationships start, stop, and start up again, then stop, and start (you get the point). The females on this show are strong physically, but when it comes to men, they pretty much will put up with anything and take anyone back...there are no consequences to cheating, lying, etc. It's not the end of the world if you let your teenager watch with you, but be prepared to explain some pretty irrational romantic behaviors and to endure some bone-crunching blood-letting that is shown in more graphic detail as the show progresses. If you have a tween, the Flash *might* be a better option. I say *might* because we're only on Season 1 of that show, and who knows, since it's an Arrow spin-off, it may go the same direction with violence as it progresses. Hopefully it won't.
An important P.S.) I wish there was a click-on option on CSM under "What should other families know" that highlights body issues being a problem on a show... example, one of the main female characters loses a dramatic amount of weight in between Seasons 1 and 2 and has had significant plastic surgery that caused her to look very different... so much so that my teen asked me, "Is that the same actress?" as she looked so tiny and changed. It was sad to see such a beautiful person change herself so much, presumably because of pressure from producers that we've read/heard about for actors to be thinner. (Making an assumption here, so forgive me for doing so.) On the positive side, she regains some weight in season 3 and looks a lot healthier. There are more examples I could list, but that's the one that was the most startling. So, heads-up to parents of tweens and teenagers, there are some stereotypical Hollywood/fashion industry body-type issues in this show, unfortunately.