This chapter explores the essential role of diagnostic imaging in aesthetic and plastic surgery. It begins by tracing the history of imaging technologies from Roentgen’s discovery of X-rays to modern modalities like computed tomography (CT), magnetic resonance imaging (MRI), ultrasound, and nuclear medicine. Each technique’s principles, such as Bremsstrahlung in X-rays or Doppler effect in ultrasound, are explained alongside their specific medical language. The application of imaging in plastic surgery is detailed across preoperative planning, intraoperative guidance, and postoperative assessment, emphasizing the precision and safety it brings to procedures. Techniques like three-dimensional (3D) modeling and elastography are highlighted for their contributions to surgical planning and patient communication. Advanced methods, particularly in breast imaging, ensure detailed evaluation even in patients with implants. This chapter stresses the importance of standardization and artificial intelligence (AI) in reducing operator bias, concluding that continuous imaging innovation will further enhance outcomes in aesthetic and reconstructive surgeries.