PEBBLE BEACH, CA — Cadillac for some time now has been trying to make its cars more appealing to a younger audience.

But the Cadillac Cien concept car not only looks youthful, it looks fast and furious. The sleek and low-slung Cien, with a brute V12 engine, looks like it could go head-to-head with Ferrari and Lamborghini.

GM unveiled the Cien (Spanish for 100, acknowledging Cadillac's 100th anniversary next year) and two other edgy concepts vehicles that GM head designer Wayne Cherry calls “vision models.”

He says they boldly point where GM is trying to go.

Besides the Cien concept, GM unveiled a GMC pickup truck, with an advanced parallel hybrid engine that runs on gasoline and electricity, and a Saturn roadster with four bucket seats and a removable top.

The Cien is probably the wildest of the bunch because of its slick areodynamic design, awesome engine and its marked contrast to the stereotype of a big-boat Cadillac piloted by a septuagenarian.

Appealing to younger buyers, BMW, Lexus and Mercedes-Benz in recent years have taken market share from Cadillac in the luxury segment. The Cien represents Cadillac's determination to fight back with a vehicle that's patterned after the F-22 Stealth fighter jet.

“Cadillac is a controversial brand to some people, but it will grow,” says Simon Cox, the Cien's chief designer and executive director of GM advanced designing in England.

“Cadillac has a lot of heritage, but, with the Cien, we wanted to express Cadillac as a modern brand,” says Mr. Cox. “It's not retro. We didn't want to go that route.”

The V12 750 h.p. engine is located toward the back of the two-seater, and is visible through the rear window. The new Northstar aluminum engine features displacement on demand, meaning it runs on six cylinders at times to save fuel.

A bank of air inlets cools the front-mounted radiators. Side air intake and exhaust vents lay flush with the surface of the car, opening up as required. The body and chassis are a lightweight carbon fiber composite.

The GMC Terra4 concept pickup truck is distinctive because of what's in front and back.

In front is a 285-h.p. 5.3L parallel hybrid V8 engine. It provides 10%-15% better fuel economy, mainly because it shuts off gas consumption when the vehicle is at rest.

At a stoplight, the gas engine shuts off, but the accessories continue working on stored electrical power.

The electrical power comes from three lead-acid batteries powering a 4.8-kilowatt motor/generator. It's integrated into the drivetrain between the gas engine and the transmission. It provides starting power and the ability to generate electricity during deceleration. A conventional starter and alternator are no longer needed.

In back is a truck bed with features that come from “our rethinking what a cargo box can be,” says Carl Zipfel, the Terra4's chief designer.

Power retractable aluminum slats can cover the bed or expose it when they fold up. Quarter panels slide up and down for side access to the truck bed.

Mr. Zipfel says the truck market has undergone a radical shift from strictly work vehicles to personal-use vehicles. But, he adds, as trucks have become more upscale — even prestigious — functionality remains supremely important.

“GMC raises these elements to new heights in the Terra4 — a four wheel-drive, four wheel steer truck with four doors and four ways to access the cargo area,” he says.

The Saturn Sky concept car aims square at the youth market. “The Sky is not too big, but big enough to carry friends and stuff,” says designer David Smith. “It's a reaction to what young people told us they wanted.”

He says GM research by its Innovative, Smart Youth Strategies team confirmed that the old assumptions of what young people wanted were outdated.

Unlike the generation before, that longed for a two-seater roadster that was “cool” but not necessarily practical, the current young generation wants something both fun and functional, says Mr. Smith.

The car's instrumentation is in the center where every passenger can see it. Headrests are arches, rather than solid designs, so that conversations can flow more easily from front and back.

The multi-piece lift-off roof is a translucent material that mutes the sunlight coming inside the vehicle. The collapsible roof stows in the rear of the vehicle.

The Sky's tonneau converts the vehicle into a snazzy two-seater, in the absence of rear-seat passengers. That's a vintage feature: the 1962 Ford Thunderbird convertible had just such a cover.

The concept Sky features a supercharged 2.2L four-cylinder engine, a five-speed manual transmission and 180 horsepower.