The relative stability of the two noradrenaline conformers AG1a and GG1a has been computed using MP2 and df-LMP2 (density-fitting local MP2) with basis sets up to aug-cc-pVQZ. For all method/basis-set combinations, the AG1a/GG1a energy gap is very small. Different basis set series show different convergence trends: for example, basis set enlargement favours AG1a in the MP2/cc-pVnZ series, but favours GG1a in the MP2/aug-cc-pVnZ and df-LMP2/cc-pVnZ series. The small difference in the AG1a and GG1a OH -> N stretch frequency, predicted by DFT, practically disappears at the MP2 level of theory, thereby rendering the infrared spectrum unusable to distinguish between the two conformers. (c) 2005 Elsevier B.V. All rights reserved.