The performance (i.e., cyclone pressure drop and particle penetration curve) of small cyclones with conical contraction bodies was investigated, with the cyclone used either as the size-selective inlet of a miniature/compact particle sensor/monitor or as a personal particle sampler. Prototype cyclones having inner bodies with conical contraction angles of 0°, 15° and 30° were constructed, and their performance was evaluated at various operational flow rates (viz., 1.0–7.0 L min–1); the results indicate that a cyclone with a high body contraction angle is capable of collecting smaller particles than one with a low contraction angle at the same cyclone pressure drop. The effect of the vortex finder insertion length on the cyclone’s performance was also studied and was found to be negligible. A linear relationship between the dimensionless particle cut-off size and the annular flow Reynolds number, Reann (in the log-log plot), could be found for the studied cyclones with characteristic cyclone velocity, calculated with the assumption of conservation of angular momentum for the swirling flow in a cyclone. Compared with previous studies, cyclones with conical contraction bodies have an advantage during lower pressure drops (up to 50%) for the same dimensionless particle cut-off size.