You want a compact PC case that doesn’t sacrifice performance or airflow. Whether you’re building a sleek workstation or a powerful gaming rig, finding the right enclosure is key. We’ve evaluated two top contenders for 2026: the Lian Li O11D Mini V2 Compact ATX Mid-Tower PC and the Cooler Master Q300L V1 Micro-ATX PC Case. For those interested in even smaller builds, check our guide on best mini ITX PC cases for compact builds.

Buying Guide: What to Look for in a Compact PC Case

Form Factor Compatibility: ATX vs. Micro-ATX

Your motherboard size determines which cases you can use. The Lian Li O11D Mini V2 supports standard ATX, M-ATX, and Mini-ITX boards, with special optimization for ATX Back-Connect motherboards. The Cooler Master Q300L V1 is designed for Micro-ATX and Mini-ITX, making it ideal for budget-friendly builds. If you need a true small form factor, explore our best micro ATX PC cases.

Airflow and Cooling Performance

Compact cases can trap heat, so efficient airflow is critical. The Lian Li O11D Mini V2 features a 10° slanted bottom design that enhances direct cold air intake and improves GPU cooling. It supports horizontal and vertical GPU anti-sag brackets. The Cooler Master Q300L V1 uses a perforated design on all sides with magnetic dust filters, and can accommodate a 240mm liquid cooler and up to five fans. For more on cooling, see our top PC cases for airflow and silence in 2026.

Build Quality and Design

The Lian Li O11D Mini V2 offers pillar-less tempered glass front and side panels for an unobstructed view. Its protruded mesh side panel accommodates full-sized ATX power supplies while keeping a compact footprint. The Cooler Master Q300L V1 has an edge-to-edge transparent side panel and a modular I/O panel that can be repositioned. Both cases are built to last, but the Lian Li stands out for premium aesthetics.

Expansion and Clearances

Check component clearance before buying. The Lian Li O11D Mini V2 includes special brackets for the 24-pin motherboard cable to keep a tidy layout. The Cooler Master Q300L V1 supports CPU coolers up to 159mm, GPUs up to 360mm, and PSUs up to 160mm. If you need more space, consider a best mini tower PC cases for compact builds.

Final Thoughts

Both cases excel in their own right. The Lian Li O11D Mini V2 is perfect if you want an ATX-compatible compact case with outstanding airflow and a showpiece design. The Cooler Master Q300L V1 is a budget-friendly option that still delivers great cooling and flexibility for Micro-ATX builds. For a premium compact build, go with the Lian Li O11D Mini V2 Compact ATX Mid-Tower PC. If you prefer a smaller, more affordable solution, the Cooler Master Q300L V1 Micro-ATX PC Case won’t disappoint. Visit our PC Cases category for more options.

Frequently Asked Questions

What is the best compact PC case for ATX motherboards?

For ATX builds, the Lian Li O11D Mini V2 is a top choice in 2026. It supports standard ATX boards and offers excellent airflow with its slanted bottom design. It also accommodates full-sized power supplies and large GPUs.

Can a compact PC case fit a full-size GPU?

Yes, many compact cases can. The Cooler Master Q300L V1 fits GPUs up to 360mm, while the Lian Li O11D Mini V2 includes anti-sag brackets for heavy graphics cards. Always check your GPU length against the case’s maximum clearance.

How important is airflow in a compact case?

Airflow is crucial in compact cases because components are closer together. Both cases we reviewed prioritize thermal performance: the Lian Li uses a slanted intake design, and the Cooler Master has a fully perforated chassis. For more tips, read our top PC cases for airflow and silence in 2026.

Are compact PC cases harder to build in?

They can require more planning, but modern compact cases like these are designed for easy assembly. The Lian Li O11D Mini V2 has cable management brackets, and the Cooler Master Q300L V1 offers a modular I/O panel. Take your time and organize cables for good airflow.