The kaonic <sup>3sup>He and <sup>4sup>He transitions in gaseous targets were observed by the SIDDHARTA experiment. The X-ray energies of these transitions were measured with large-area silicon-drift detectors using the timing information of the pairs produced by the DA¦µNE collider. The strong-interaction shifts and widths both of the kaonic <sup>3sup>He and <sup>4sup>He 2p states were determined, which are much smaller than the results obtained by the previous experiments. The ¡°kaonic helium puzzle¡± (a discrepancy between theory and experiment) was now resolved.