Star mutual fund investor Peter Lynch used to say that companies “deworsified” when they acquired other companies that were a bad fit.

So it stands to reason that the opposite would be true: Badly fitting subsidiaries that get spun off should make good investments, right?

Now there’s a new exchange-traded fund dedicated to that theory. The Claymore/Clear Spin Off ETF (CSD) invests solely in recent spin-offs. It consists of the 40 “highest-ranking” stocks chosen from the universe of companies that have been spun off within the last two years, according the fund’s prospectus.

That measure of “highest-ranking” is a bit of a black-box mystery, but management firm Claymore Advisors says it uses “growth-oriented” filters in its scoring.

Is this a strategy work pursuing? Maybe so, if you like what companies like Kraft, Toys R Us, Chaparral Steel and Western Union have done in the past. Those spin-offs did spectacularly well, at least for a while, after their parent companies spun them off.

Western Union, for example, was spun off by First Data last October; it was up 26 percent in the two months that followed. Chaparral Steel has gone up six-fold since it was spun off by Texas Industries Inc. in July 2005.

There’s also a lot of academic research saying that spin-offs tend to do well. It may be because the spun-off company is out of the shadow of its bigger owner and is free to pursue profitability on its own. Or it may be because the spun-off company’s managers now feel more pressure to create bottom-line performance. Whatever the reason, spin-offs tend to work.

There’s some evidence of that in the returns of the one traditional mutual fund that focuses on spin-offs. Keeley Small Cap Value Fund (KSCVX) has returned an average of 19 percent annually for five years running, practically tripling the Standard & Poor’s 500 index over the same period, according to Morningstar.

Keeley also includes some bankruptcy-emerging and restructuring companies, but demonstrates what the spin-off sector can do. (With a 4.5 percent upfront load and annual fees of 1.39 percent, it’s a lot more costly than the Claymore ETF, which claims a 0.69 percent expense ratio.)

Investors who want to play this concept might invest in this ETF, but it’s not something you would do with the core of your nest egg. It might be a bet around the edges of a well-diversified portfolio.

Another approach, for folks who like to buy individual stocks, might be to steal some of the Claymore ideas: Its biggest holdings, according to its most recent report, include Embarq Corp., Ameriprise Financial, Disca US, Expedia, Mosaic Co., CBS Corp. and CNX Gas Corp.

There’s one other tactic worth mentioning. Companies that spin off misfit subsidiaries tend to do pretty well themselves.

After all, McDonald’s just reported fourth-quarter earnings that were almost double those of a year earlier, and it credited its spin-off of Chipotle. So instead of buying the spun-out, you could look to the spinners for future profits.

(Linda Stern is a freelance writer. Any opinions in the column are solely those of Ms Stern. You can e-mail her at lindastern[AT]aol.com.)