BOSTON (TheStreet) -- The Under the Radar Portfolio of TheStreet's 10 favorite small-cap stocks has returned 23% since their original recommendations. Seven have delivered double-digit percentage gains in the first quarter.

Generic drugmaker

Perrigo

(PRGO) - Get Report

has soared 44% since we recommended it on Jan. 25.

Snack food specialist

Diamond Foods

(DMND)

has surged 39% since

TheStreet's

pick on Oct. 28.

High-tech component maker

Spectrum Control

(SPEC)

has returned 37% since our Feb. 4 article.

Bucyrus

( BUCY),

Carbo Ceramics

(CRR) - Get Report

and

Conseco

(CNO) - Get Report

have all risen more than 20% since our picks.

Touch-screen maker

Synaptics

(SYNA) - Get Report

has gained 11%, but has been dogged by sell-side downgrades recently.

Einstein Noah Restaurant Group

(BAGL)

has risen 4.2%.

Once a portfolio leader,

Telestone Technologies

(TSTC)

has plummeted 18% during the past month, bringing its gain to 4.6%. Investors are awaiting fourth-quarter results.

China North East Petroleum

(NEP) - Get Report

has fallen out of favor since we recommended it. The stock is down 2%, thought it has rebounded in the past week. On Wednesday, the shares popped 7.4%. Management was forced to revise its 2008 and 2009 financial statements to account for non-cash accounting adjustments. Investors had enjoyed a gain of 563% over the past year.

China North remains a fundamentally attractive investment and we are sticking with the stock. The company's recently purchased oilfield-services subsidiary Song Yuan Tiancheng Drilling Engineering just signed a contract with

PetroChina

(PTR) - Get Report

to drill 30 wells, its second large new contract of 2010. Furthermore, with China's economy demonstrating resilience and crude oil hitting a 17-month high this week, China North is a solid bet.

China North's low-cost drilling strategy translates to a net margin consistently between 30% and 40%. Its third-quarter net spread hit 33%, beating those of

Exxon Mobil

(XOM) - Get Report

,

Chevron

(CVX) - Get Report

and

ConocoPhillips

(COP) - Get Report

. In addition, its balance sheet and valuation are far superior to U.S. large-cap peers. China North holds $33 million of cash and $12 million of debt, translating to a quick ratio of 1.4 and a debt-to-equity ratio of 0.2.

With a market value of $234 million, China North hasn't attracted a large Wall Street following, so its shares are still undervalued. It trades at a price-to-projected-earnings ratio of 7.2 and a price-to-cash-flow ratio of 6.6, 50% and 32% discounts to peer-group averages. It's also cheap based on trailing earnings and book value.

Rodman & Renshaw

(RODM) - Get Report

, which rates China North "buy," expects the stock to advance 13% to $11.

China North's shareholders are bullish on its prospects, with 14, or 70%, of the 20 largest increasing their bets during the fourth quarter while four retained their positions and one decreased its holdings. On March 17, roughly 1,500 call options were traded and just 150 puts, indicating that investors are betting on China North's upside. A heavy proportion of call buying is often a signal of near-term gains.

View the Under-the-Radar Portfolio

-- Reported by Jake Lynch in Boston.