H-scan ultrasound (US) is an innovative real-time imaging technology that depicts the relative size of acoustic scattering objects and structures. The purpose of this research was to develop a novel 3-dimensional (3D) H-scan US imaging approach for tissue classification in volume space. Using a programmable research scanner (Vantage 256, Verasonics Inc, Kirkland, WA) equipped with a custom-built volumetric imaging transducer (4DL7, Vermon, Tours, France), radio frequency (RF) data was collected for offline processing. H-scan US images were constructed after applying a set of convolutional filters based on Gaussian-weighted Hermite polynomials. These functions are related to different sized scattering objects. Preliminary studies were conducted using homogeneous gelatin-based tissue-mimicking phantom materials embedded with acoustic scatterers of varying size (15, 30 or 250 μm) and concentrations (0.1, 0.3, 0.5 or 1.0 %). In vitro results indicate that 3D H-scan US imaging can detect acoustic scatterers of varying size (p < 0.01) and independent of scatterer concentration (p > 0.05). Overall, our preliminary in vitro findings reveal that 3D H-scan US imaging allows the visualization of different tissue scatterer patterns.