This ESR Essentials article intends to provide detailed, step-by-step, information on the role of imaging in the diagnosis, procedural management, and follow-up of patients with fluid collections. Evidence-based medicine recommendations for the positioning of percutaneous drainages and/or for diagnostic/therapeutic aspiration of fluid collections are provided. Although medical history, clinical symptoms, physical examination, and laboratory tests can raise suspicions regarding a collection, an imaging assessment is usually necessary for the diagnosis. Radiologists can easily identify fluid collections that are clinically suspected by using a wide range of imaging modalities, such as ultrasound, CT, MRI, and cone-beam CT. Consequently, these imaging methods (either alone or combined), can be used to aspirate the collection or for the placement of a drainage catheter. The choice of imaging technique to be used is influenced by the location of the collection, operator preference, size, and content of the collection. In addition, it is of utmost importance to underline the role of the interventional radiologist in the management and follow-up of patients with percutaneous drains, in collaboration with surgeons, clinicians, and diagnostic radiologists. KEY POINTS: Indications for percutaneous imaging-guided drainage are supported by clinical findings, laboratory tests, and pre-procedural imaging. Deciding between aspiration or drain insertion should follow patient assessment and fluid collection characterization. The interventional radiologist should be part of the entire patient care process including follow-up.