We prove preservation of L q dimensions (for 1 < q ≤ 2) under all orthogonal projections for a class of random measures on the plane, which includes (deterministic) homogeneous self-similar measures and a well-known family of measures supported on 1-variable fractals as special cases. We prove a similar result for certain convolutions, extending a result of Nazarov, Peres and Shmerkin. Recently many related results have been obtained for Hausdorff dimension, but much less is known for L q dimensions.2000 Mathematics Subject Classification. Primary 28A80, Secondary 28A78, 37H99.[8]). In general, q → D q may be strictly decreasing (this is a reflection of the multifractality of µ), but it may also be constant. For example, if µ is Ahlforsregular with exponent d (that is, if C −1 r d ≤ µ(B(x, r)) ≤ C r d for all x ∈ supp(µ)) then D q µ = dim H µ = d for all q. For many measures of dynamical origin, such as self-similar measures, the limit in the definition of D q is known to exist, see [22].The only previous result on L q dimensions of projected measures was obtained in [19]. There it is proved that if µ, ν are self-similar measures satisfying certain natural assumptions, then for any q ∈ (1, 2], D q (Π(µ × ν)) = min(D q (µ × ν), 1)