  We have used HST/NICMOS H-band narrow-band Pa-alpha (at rest 1.87micron)
images to identify star clusters and HII regions respectively in a sample of 8
luminous infrared galaxies (LIRGs). These observations have revealed the
presence of a large population of super star clusters (SSC) and bright HII
regions. A significant fraction of the HII regions shows H-alpha luminosities
above that of 30 Doradus, the prototypical giant HII region. The excess of
extremely luminous HII regions in LIRGs has been confirmed by comparison with
normal galaxies observed at similar spatial resolutions. Despite the large
numbers of identified star clusters and HII regions in LIRGs, we only find a
small fraction of coincidences, between 4% and 30%. Using synthesis models we
have reproduced the relative fractions of young HII regions, intermediate and
old star clusters observed in Arp299 and the central region NGC3256 using a
Salpeter IMF and instantaneous star formation. HII regions with no detected
near-infrared cluster counterpart (25-39%) represent the youngest sites of star
formation, with ages of up to approximately 5Myr and mostly intermediate mass
(~10^5Msun) ionizing clusters. For these two galaxies, and within the present
detection threshold we can only detect coincidences (4-10%) between an HII
region and a near-infrared star cluster for the most massive star clusters
(~10^6Msun) during the first 7Myr of their evolution. The identified
near-infrared SSCs with no detectable Pa-alpha emission represent the ``old''
population (53-66% of the detected sources), with ages of between 7 and
20-40Myr. Older clusters possibly created in this or previous episodes of star
formation are likely to exist in these systems but cannot be identified with
the present detection threshold. (Abridged)
