The performance (i.e., cyclone pressure drop and particle penetration curve) of small cyclones with conical contraction bodies was investigated either as the size-selective inlets of miniature/compact particle sensors/monitors or as personal particle samplers. Prototype cyclones having inner bodies with the conical contraction angles of 0°, 15° and 30° were constructed and their performance was evaluated at various operational flowrates (i.e., 1.0-7.0 lpm). The effect of vortex finder insertion length on the cyclone performance was also studied. It is found that the cyclone with a high body contraction angle is capable of collecting smaller particles than ones with low body contraction under the same cyclone pressure drop. The effect of vortex finder insertion length on the cyclone performance was found 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 studied cyclones with the cyclone characteristic velocity, calculated by the assumption of the conservation of angular momentum for swirling flow in a cyclone. Compared with those previous studies, cyclones with conical contraction bodies have the advantage on lower pressured drop (up to 50%) for the same particle cut-off size.