\usepackage {pstricks}
\begin{pspicture}(0,0)(4.2,6.2)
\pstextpath[l]
{\pscurve(0,0)(2,2)(4,0)}
{Left justified}
\pstextpath[c]
{\pscurve(0,2)(2,4)(4,2)}
{Centred text}
\pstextpath[r]
{\pscurve(0,4)(2,6)(4,4)}
{Right justified}
\end{pspicture}