The paper describes the design of optimized PCB air-core toroids for high frequency DC-DC converters with strict requirements in terms of volume and noise. The effect of several design parameters on the overall inductor volume, on DC and AC winding resistance, and on the radiated noise will be investigated. PCB toroids are compared to standard air-core solenoids and other state-of-the-art air-core toroids both theoretically and experimentally: at first using ANSOFT Maxwell and ANSOFT Q3D simulation tools, subsequently with laboratory measurements (irradiated noise and efficiency) on several prototypes. These very flexible and rather easy to manufacture inductors appear very attractive for compact high frequency DC-DC converters where high efficiency, low volume and low noise are of primary concern. © 2009 IEEE.